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  • 1
    Electronic Resource
    Electronic Resource
    Iridoviruses associated with epizootic haematopoietic necrosis (EHN) in aquaculture (1997)
    Springer
    World journal of microbiology and biotechnology 13 (1997), S. 367-373 
    Details
    ISSN: 1573-0972
    Keywords: Amphibian ; aquaculture ; epizootic haematopoietic necrosis virus ; fish ; frog virus 3 ; Iridoviridae ; ranavirus ; reptile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Systemic infections of teleost fishes caused by iridoviruses have recently been recognized in Australia, Asia, Europe and the USA. These iridoviruses are different from those of the established genera Lymphocystivirus and Goldfish Virus 1-like Viruses of the family Iridoviridae. The agents exhibit similar physicochemical properties, are antigenically related and prove to be of high virulence to different teleost fishes in aquaculture. The first iridovirus, epizootic haematopoietic necrosis virus, responsible for an epizootic outbreak of haematopoietic necrosis in redfin perch, was reported in Australia. Some years later, similar iridovirus epizootics occurred in sheatfish and catfish in Europe. The Australian and the European isolates proved to be antigenically related and showed properties in common with frog virus 3, the type species of the genus Ranavirus of the Iridoviridae. Further iridovirus isolates from fish, amphibians and reptiles exhibited a close relationship with each other and with frog virus 3. It is important to note that the Australian amphibian iridovirus, Bohle iridovirus, was experimentally transmitted to teleost fish inducing high mortalities. The occurrence of similar viruses in different host species in the aquatic environment and their inter-species transmission emphasize the importance of health control in aquaculture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018563930712
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  • 2
    Electronic Resource
    Electronic Resource
    A Connectionist Model of Left-Right Sound Discrimination by the Mauthner System (1999)
    Springer
    Journal of computational neuroscience 6 (1999), S. 121-144 
    Details
    ISSN: 1573-6873
    Keywords: Mauthner ; escape ; artificial neural networks ; connectionism ; acoustic ; localization ; auditory ; fish ; goldfish ; XNOR model ; phase model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract Artificial neural networks were used to explore the auditory function of the Mauthner system, the brainstem circuit in teleost fishes that initiates fast-start escape responses. The artificial neural networks were trained with backpropagation to assign connectivity and receptive fields in an architecture consistent with the known anatomy of the Mauthner system. Our first goal was to develop neurally specific hypotheses for how the Mauthner system discriminates right from left in the onset of a sound. Our model was consistent with the phase model for directional hearing underwater, the prevalent theory for sound source localization by fishes. Our second goal was to demonstrate how the neural mechanisms that permit sound localization according to the phase model can coexist with the mechanisms that permit the Mauthner system to discriminate between stimuli based on amplitude. Our results indicate possible computational roles for elements of the Mauthner system, which has provided us a theoretical context within which to consider past and future experiments on the cellular physiology. Thus, these findings demonstrate the potential significance of this approach in generating experimentally testable hypotheses for small systems of identified cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008828501676
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  • 3
    Electronic Resource
    Electronic Resource
    A fishery in a changing lake environment: The naked carpGymnocypris przewalskii (Kessler) (Cyprinidae: schizothoracinae) in Qinghai Hu, China (1995)
    Springer
    International journal of salt lake research 4 (1995), S. 169-222 
    Details
    ISSN: 1573-8590
    Keywords: China ; Qinghai ; Koko Nor ; Cyprinidae ; fish ; fishery ; recruitment ; spawning ; catch per unit effort ; management ; translocation ; saline lake ; dryland ; semi-arid ; irrigation ; conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Quinghai Hu is a large, high-altitude, saline lake in north-western China, and supports a fishery based on an endemic species of naked carp (‘snow trout’). The fish take seven years to attain maturity and a marketable weight of 300 g, and have a lifespan of 14–21 years under the present fishery regime. They seasonally migrate from the lake to spawn over the gravel beds of inflowing rivers, but these areas have been reduced by weirs and irrigation diversions and recruitment may have declined. The population may have been affected also by a 1.85-m fall in the lake level over the past 30 years, and by associated changes in salinity. The fishery was opened to large-scale exploitation in 1958. Yields declined sharply (max. 28,523 tonnes, 1960) as the larger, older fish were removed, and then more slowly (min. 2523 tonnes, 1983). Since 1987 the fish factory has been limited to an annual quota of 1200 tonnes, taken by a fleet of four pair trawlers. Another 800 tonnes are taken by licensed fishermen, mainly using gill nets, and perhaps 1000 tonnes are taken illegally. The estimated total catch in 1992 was 3000 tonnes. New trawlers introduced in 1989–90 substantially increased the factory's catch per unit effort, and in 1990 the quota was virtually filled in one month in a zone within 20 km of the factory. Although this could suggest that the stocks will be conserved if the quota is retained, at least half of the catch in 1989–92 consisted of immature individuals. Trawling operations recently were suspended following a further decline in the catch after 1992. While the new trawlers are capable of a major increase in effort, neither the changing environment, the fish stocks or the present markets favour intensified pressure. Gillnets may provide better control over the minimum size limit and may cause less damage than trawling. Other options to improve the viability and profitability of the fishery include improvements in handling, processing and marketing. Failure to develop the fishery may encourage attempts to introduce exotic fish, at some risk to survival of the local species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02001491
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  • 4
    Electronic Resource
    Electronic Resource
    Critical comparison of methods for mercury determination in fish (1995)
    Springer
    Microchimica acta 119 (1995), S. 305-310 
    Details
    ISSN: 1436-5073
    Keywords: mercury ; fish ; collaborative study ; atomic absorption spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract One of the major analytical problem in the analysis of fish tissues for total mercury is the dissolution of the sample. This paper compares two different methods of wet digestion (microwave and closed pressurized vessel), followed by FIAAS as final determination and a Zeeman-solid-sample-AAS determination method without previous mineralization. Six fish samples were selected for this study. The top, the central and the bottom portions of the fish were analyzed separately. The mercury contents in the bottom portions determined by Zeeman-solid-sample-AAS were significantly higher than those obtained by the other two systems. A good correlation was observed among the results of the different techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244010
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of open and closed focussed microwave digestions in view of total mercury determination by cold vapour atomic absorption spectrometry (1995)
    Springer
    Microchimica acta 119 (1995), S. 199-209 
    Details
    ISSN: 1436-5073
    Keywords: microwave digestion ; fish ; mercury ; CVAAS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Food samples digestion, in view to quantify total mercury, is the first step to perform before measuring mercury by cold vapour atomic absorption spectrometry (CVAAS). We have compared two microwave digestion systems, one working at atmospheric pressure (open system) and the other one under pressure (closed system). Results obtained for fish muscle samples by the two methods are in good agreement. However, fat is not digested in the open system, whereas in the closed system no more fat remains in the final solution. During the quantification step, applying the CVAAS technique, we have noticed that the choice and the concentration of the reductant solution is very important to obtain good results. Elaborated methods have been validated using certified reference materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01243999
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  • 6
    Electronic Resource
    Electronic Resource
    Interspecific variation in sustained swimming ability of late pelagic stage reef fish from two families (Pomacentridae and Chaetodontidae) (1998)
    Springer
    Coral reefs 17 (1998), S. 111-119 
    Details
    ISSN: 1432-0975
    Keywords: Key words Dispersal ; coral reefs ; fish ; swimming ; Larvae ; Juveniles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  Characteristics of the pelagic stages of reef fishes have generally been investigated at the family level, which may mask important differences among species. Here the variation in sustained swimming ability of the late pelagic stages is examined among species, within two families (Pomacentridae and Chaetodontidae). The pomacentrids displayed a 7.5-fold difference in sustained swimming ability across 24 species, while the chaetodontids displayed a 2-fold difference across 10 species. The variation within the Pomacentridae was not related to pelagic larval duration, post-settlement habitat or taxonomy. There was, however, a significant correlation between sustained swimming ability and total length (TL) of individuals (r=0.435, P〈0.0001). Differences in the mean distance swum by pomacentrid species, however, was most strongly related to differences in mean wet weight (r=0.814, P〈0.0001). When the mean distance swum by species was scaled with respect to mean TL there was still a strong correlation with mean wet weight (r=0.644, P〈0.005). Among chaetodontid individuals TL and sustained swimming ability were not correlated (r=−0.004, P=0.978). Furthermore, sustained swimming ability was not significantly related to the trans-oceanic distribution of species in either family. The variation in sustained swimming ability, however, may contribute to explanations of the observed levels of gene flow within populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003380050104
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  • 7
    Electronic Resource
    Electronic Resource
    Divergent distributions of prey and predator, a fishing effect? (1995)
    Springer
    Aquatic sciences 57 (1995), S. 106-118 
    Details
    ISSN: 1420-9055
    Keywords: Benthos ; fish ; vertical distribution ; predation risk ; selective fishing ; Lake Constance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To compare the vertical distributions of benthos and fish species of Upper Lake Constance (Bodensee), 552 benthos samples were taken with an Auerbach grab at four transects (10–250 m). An additional 54 samples (1–10 m) were collected elsewhere. Complementary data was taken from the literature. In winter, most fish feed on benthos, mainly chironomids, but in summer less than 5% do so. Formerly the bottom gill-netting aimed mainly at catchingCoregonus pidschian, but it now aims atPerca fluviatilis. Contrary to expectation, in winter the greatest abundance ofP. fluviatilis is much deeper (55 m) than that of its preferred food, i.e. chironomids (〈20 m). Comparably,C. pidschian also stayed deeper than its main food source (chironomids and mollusks).Lota lota, Salvelinus profundus andS. alpinus — unlike the unwanted cyprinids — also stay or stayed deeper than the attractive chironomids. It is argued that the fish reduce their “predation risk”, i.e. the risk of being gillnetted in the upper 50 m, by “selecting” the deeper less dangerous, but also less food-abundant habitat. Balancing predation risk against food abundance may have led to “survival of the deepest”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877379
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  • 8
    Electronic Resource
    Electronic Resource
    Prevalence and abundance of two trematode parasites,Diplostomum phoxini andMacrolecithus papilliger in European minnows (Phoxinus phoxinus) in an artificial Swiss Alpine lake (1995)
    Springer
    Aquatic sciences 57 (1995), S. 119-126 
    Details
    ISSN: 1420-9055
    Keywords: Phoxinus phoxinus ; fish ; Diplostomum phoxini ; Macrolecithus papilliger ; parasitism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of parasites on the breeding biology of the European minnow (Phoxinus phoxinus) was studied by examining 268 adult and 59 young-of-the-year minnows from an artificial Swiss Alpine lake for parasites during the breeding seasons in 1990 and 1991. Two trematode parasites;Diplostomum phoxini, in their brains, andMacrolecithus papilliger, in their guts, were found. The prevalence ofD. phoxini was 100% in both years. The mean abundance was 231 in 1990 and 448 in 1991; the difference was significant. Prevalence (and abundance) ofM. papilliger was 37.5% (1.04±0.39) in 1990 and 59.5% (2.68±0.55) in 1991; also significantly higher in 1991 than in 1990. No differences in prevalence or abundance between males and females were found. Numbers of both parasites were significantly correlated with fish length. There was seasonal variation in the abundance ofD. phoxini metacercariae, with a peak in June/July in both years. The prevalence ofM. papiller decreased after July in both years. Distribution of the two trematodes was overdispersed as indicated by the variance to mean (abundance) ratio. The observed seasonal variation inD. phoxini abundance also suggests that sublethal parasites could influence the population dynamics of their hosts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877380
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of chronic heat stress on cortisol levels in the antarctic fishPagothenia borchgrevinki (1995)
    Springer
    Cellular and molecular life sciences 51 (1995), S. 768-774 
    Details
    ISSN: 1420-9071
    Keywords: Cortisol ; stress ; heat ; Antarctic ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Radioimmunoassay was used to determine levels of the stress-inducible glucocorticoid, cortisol, circulating in the plasma of the extremely stenothermal Antarctic fishPagothenia borchgrevinki at rest and after heat stress. Fish sampled immediately after capture (−1.9°C) had low cortisol levels (10.4±1.4 ng ml−1, mean±SEM) as did fish which were laboratory rested for 3 days. Sudden exposure to 5°C (48h) resulted in a peak cortisol value after 3 h (69.9±6.8 ng ml−1) whereas exposure to 8°C (6h) resulted in a peak value after 1 h (73.5±8.0 ng ml−1). At both temperatures levels remained significantly elevated (p〈0.05) for the entire period of exposure. Increased temperature also resulted in a significant change in haemoglobin, haematocrit and mean cell haemoglobin concentration (MCHC) (p〈0.05). Plasma lactate was significantly elevated only after exposure to 8°C (p〈0.05). Plasma cortisol levels fromP. borchgrevinki are reported here for the first time and show this cryopelagic Antarctic species to have an unusual hormonal stress profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01922428
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  • 10
    Electronic Resource
    Electronic Resource
    Negative Impact on the Aquatic Ecosystems of the State of Morelos, Mexico from Introduced Aquarium and Other Commercial Fish (1998)
    Springer
    Aquarium sciences and conservation 2 (1998), S. 67-78 
    Details
    ISSN: 1573-1448
    Keywords: fish ; introductions ; management ; México ; native species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Of the 22 fish species presently inhabiting the waters of the state of Morelos, México, more than half (64%) have been introduced, mainly for fisheries and ornamental aquaculture purposes. Even though there are other significant problems such as pollution, eutrophication and drought, we found that fish introductions have caused the worst ecological impacts. These problems stem from a general lack of knowledge regarding the characteristics, importance and appropriate use and management of aquatic resources. Conservational actions are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009676403693
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  • 11
    Electronic Resource
    Electronic Resource
    Plasma concentrations of steroid hormones in male yellow perch, Perca flavescens: the effect of age and photothermal manipulation (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 97-105 
    Details
    ISSN: 1573-5133
    Keywords: fish ; 11-ketotestosterone ; testosterone ; estradiol ; sperm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plasma steroid concentrations in two and three year-old male yellow perch maintained under two different photothermal regimes were investigated. Initially, all fish kept indoors were exposed to the same water temperature (22 °C) and photoperiod (15L:9D). By the end of August, following the first sampling, fish were exposed to different photothermal regimes. Groups A2 (2 year old) and A3 (3 year old) were maintained under photothermal conditions similar to those of southern Ohio. Groups B2 (2 year old) and B3 (3 year old) were exposed to a condensed light/temperature regime designed to accelerate maturation. Testosterone (T) was the major circulating androgen in all groups. In regime A fish, plasma concentrations of 11-ketotestosterone (11KT) and T were very low in August, increased in October and remained elevated until March. In regime B plasma androgens were high until February and then dropped abruptly in March. The elevated circulating levels of 11KT and T were associated with production of sperm. The highest sperm concentration in the groups A3 and B3 was observed in February and December, respectively. There were no major differences in profiles and levels of plasma steroids between two age categories within each photothermal regime. These data indicate that the compression of the photothermal cycle accelerated both the occurrence of the low postspawning levels of circulating steroids and the completion of milt production. Higher sperm concentration observed in B3 group earlier in the season compared to A3 group also support the notion that the condensed photothermal cycle accelerated gonadal maturation. It appears that modification of the environmental cues may be a useful tool for manipulation of reproductive processes in male yellow perch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007460630535
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  • 12
    Electronic Resource
    Electronic Resource
    Physiological tolerances of juvenile robust redhorse, Moxostoma robustum: conservation implications for an imperiled species (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 429-444 
    Details
    ISSN: 1573-5133
    Keywords: fish ; Catostomidae ; temperature ; salinity ; pH ; hypoxia ; conservation biology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The robust redhorse, Moxostoma robustum (Teleostei: Catostomidae), is an imperiled sucker native to large rivers of the Atlantic slope of the southeastern United States. Juvenile M. robustum were tested for tolerances to temperature, salinity, pH, and hypoxia in order to evaluate basic early life-history requirements. Static (acute) tests resulted in estimates of mean lower temperature tolerances (5.3–19.4 °C) that varied with prior thermal acclimation and indicated no apparent difference in tolerance among fish 30, 60, and 90 days old. Fish acclimated to 20 °C and 30 °C had significantly different mean critical thermal maxima (34.9 °C and 37.2 °C, respectively) and exhibited pronounced increased opercular ventilation rates with elevated temperatures. Fish exposed to acute and chronic increases in salinity showed unusual patterns of mortality above the isosmotic point (9 ppt) that reflected possible differences in body mass and prior acclimation conditions (i.e., water ionic composition); small fish and those held in soft water were the least tolerant of increased salinity. Abrupt exposure to extreme pH values resulted in greater than 50% mortality at pH values below 4.3 and above 9.5 within a 96-hour period. Fish exposed to progressive hypoxia utilized aquatic surface respiration at a mean oxygen concentration of 0.72–0.80 mg O2 l-1 (20 °C and 30 °C acclimated fish, respectively), and lost equilibrium at 0.54–0.57 mg O2 l-1. Juvenile M. robustum are moderately tolerant of a wide range of ambient physicochemical parameters, but further research is needed to determine how both abiotic and biotic factors have contributed to population decline and extirpation of this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007486632102
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  • 13
    Electronic Resource
    Electronic Resource
    Generalists as sequential specialists: diets and prey switching in juvenile silver perch (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 445-454 
    Details
    ISSN: 1573-5133
    Keywords: planktivory ; insectivory ; pond fertility ; fish ; Bidyanus bidyanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diets of silver perch, Bidyanus bidyanus, in organically fertilised aquaculture ponds were dominated by chironomid larvae, Daphnia and calanoid copepods. Insects and crustaceans contributed approximately 80% and 20% by weight to the diet respectively. Classification of the stomach contents of individual fish revealed 8 diet groups, 4 of which were dominated by planktonic crustaceans and 4 by insects. Each diet group was strongly dominated by a different prey type. Fish from the same sample tended to belong to the same diet group and there was a non-random distribution of diet groups across ponds. Perch diets were influenced by the method of pond fertilisation (livestock effluent or pellet feed). Shifts in the representation of groups indicated that fish switched from one diet group to another over a 2–4 week period. The selection of planktonic prey by perch was related to prey densities in the ponds. Fish preferred Daphnia when these prey were common, but switched to calanoids and insects when Daphnia were scarce. A perfect rank correlation between the mean body size of planktonic prey and their contribution to the diet suggested that prey choice involved comparative decisions based on prey size. These findings indicate that, while classified as dietary generalists, silver perch exhibit consumption patterns which at the individual level are highly specialised at any given time. These patterns can be predicted, given information on prey densities in the environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007489100809
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  • 14
    Electronic Resource
    Electronic Resource
    Factors affecting the duration of nest defense and reproductive lifespan of female sockeye salmon, Oncorhynchus nerka (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 369-375 
    Details
    ISSN: 1573-5133
    Keywords: fish ; longevity ; parental care ; salmonid mating systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproductive success of female animals is often affected by a combination of fecundity and parental care. In female salmonid fishes, acquisition of nest (redd) sites and prevention of their use by other females are critical to reproductive success. These factors are particularly important for stocks that spawn at high densities. Body size is positively correlated with fecundity and egg size, and has been hypothesized to control the outcome of intrasexual competition and longevity. We tested this hypothesis by evaluating the influences of body size, intrasexual aggression and arrival date on duration and success of redd guarding by female sockeye salmon, Oncorhynchus nerka, in a small Alaskan creek. Contrary to the hypothesis, larger females guarded their redds no longer than smaller females, and did not live as long in the stream. Aggression was not related to body size or overall longevity but was positively correlated with residence period on the redd. Females that entered the creek earlier lived longer, spent longer on their redds, and spent more time guarding their redds after spawning than females that entered the creek later. However, despite their longevity, early-arriving fish were more likely to have their redds reused by another female because they died before all the females had selected redd sites. The small average body size in this stock is consistent with weak selection for large size, and with our evidence that size provided little if any advantage in nest guarding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007432928783
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  • 15
    Electronic Resource
    Electronic Resource
    Use of substratum ripples for flow refuging by Atlantic cod, Gadus morhua (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 455-460 
    Details
    ISSN: 1573-5133
    Keywords: station-holding ; current ; trough ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ability to maintain position in a current without actively swimming (station-holding) was measured on substratum ripples for Atlantic cod, Gadus morhua, a bentho-pelagic fusiform species. The current velocities tested ranged from 0–111 cm sec-1. Ripples were sinusoidal, with twelve combinations of ripple wavelength (10, 25, 50, 125 cm) and ripple amplitude (1.0, 2.5, 5.0 cm). Ripple wavelengths were chosen to approximate 0.5, 1.0, 2.0 and 5.0 times fish total length. The potential of ripples to locally retard current and thereby provide a refuge from the flow was measured as a velocity ratio, utrough/ufree-stream, where utrough is the flow velocity measured at a height of 0.5 cm from the bottom of a trough and ufree-stream the flow velocity measured at a height of 10 cm above ripple crests. Cod usually swam steadily above substratum ripple crests in the free-stream flow. They used substratum ripples to hold station on only 3 of the 12 ripples tested by refuging from the flow in the ripple troughs (flow refuging). These ripples had wavelengths approaching twice the body length, with ripple amplitudes that produced velocity ratios of 0.44–0.65, thus providing at least a 35% flow reduction in the troughs. In addition, these ripples were only used at intermediate velocities starting at 49–78 cm sec-1 and ending at 81–109 cm sec-1 depending on the ripple morphology, suggesting there may be costs involved in flow refuging, probably in stability control. Flow refuging on substratum ripples could dramatically impact the physiology and ecology of cod in high current velocities by providing areas of retreat for energetic savings, but also offering opportunities for enhanced feeding and migration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007449630601
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  • 16
    Electronic Resource
    Electronic Resource
    Life-history variations in the fluvial sculpin, Cottus nozawae (Cottidae), along the course of a small mountain stream (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 203-212 
    Details
    ISSN: 1573-5133
    Keywords: mark-and-recapture ; size at maturity ; age at maturity ; restricted movement ; individual growth ; sex ratio ; population density ; phenotypic plasticity ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Life-history variations in male and female fluvial sculpins, Cottus nozawae, were studied in a small mountain stream in Hokkaido, Japan, primarily by using capture-mark-recapture methods. At three study areas established along the stream course, the majority of marked sculpins were recaptured in their original location over one or more years, indicating their long-term occupation of each restricted habitat area. Sculpin densities increased toward the upstream habitats, whereas individual growth rates were more rapid downstream. In both sexes, sculpins distributed downstream matured at a larger body size and later in life than upstream sculpins, clearly demonstrating a clinal variation in these respects. A comparison of life-history variations in C. nozawae with those in amphidromous C. hangiongensis suggests that intrapopulational life-history variations in the former might be environmentally induced, and that one of the most important determinants for the variations in Cottus species might be population density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007347631573
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  • 17
    Electronic Resource
    Electronic Resource
    Sex determination system of the rosy bitterling, Rhodeus ocellatus ocellatus (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 251-260 
    Details
    ISSN: 1573-5133
    Keywords: backcross ; crossover ; gynogenesis ; meiosis ; triploid ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rosy bitterling, Rhodeus ocellatus ocellatus, is the only fish species known in which artificial triploids are always male, regardless of the kind of polyploidization technique used. In order to elucidate the genetic sex determination system of the rosy bitterling, two kinds of gynogenesis were carried out: retention of the second polar body (GRSPB) and suppression of the first cleavage (GSFC). The sex ratio of progeny was nearly 7:1 (♂:♀) for both GRSPB and GSFC, while those of control and parental fish were almost 1:1. In backcrosses of female progeny by GRSPB and normal diploid males, male progeny were observed at low frequency (one or two individuals in each experiment), except in one experiment where the appearance rate of males was about 50%. From results of gynogenesis and backcrosses, the following conclusions can be made. The genetic sex determination system of the rosy bitterling is a heterogametic female system (ZW). Survival rate of superfemales (WW), produced by gynogenesis, is much lower than that of males (ZW).There is a possibility that crossovers between sex determining genes and a centromere occur in the first meiosis. With repect to the mechanism of unisexuality (male) of artificial triploids of the rosy bitterling, only males (ZZZ and ZZW) are presumed viable, while females (ZWW) are probably inviable.
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    URL: http://dx.doi.org/10.1023/A:1007328414175
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    Are the Indonesian and Western Indian Ocean Coelacanths Conspecific: A Prediction (1999)
    Springer
    Environmental biology of fishes 54 (1999), S. 453-456 
    Details
    ISSN: 1573-5133
    Keywords: Latimeria ; fish ; distribution ; geological history ; India ; river flow ; effects of siltation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is hypothesized that the ancestor of the extant western Indian Ocean and Indonesian populations of Latimeria was continuously distributed along the deeper coasts of massed Africa–Madagascar–Eurasia in early geologic time. The collision of India with Eurasia, roughly 50 MY ago, caused the formation of the Himalayan Mountains and subsequent developement of numerous rivers. The rivers, which flow down both coasts of India, and areas even further east, deposited, and continue to deposit, great amounts of silt along both coasts of India. The siltation destroyed possible coelacanth habitats, thus isolating coelacanth populations to the west of India from those to the east and allowing them to diverge.
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    URL: http://dx.doi.org/10.1023/A:1007524929593
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    Gill Morphometry in Growth Hormone Transgenic Atlantic Salmon (1999)
    Springer
    Environmental biology of fishes 54 (1999), S. 405-411 
    Details
    ISSN: 1573-5133
    Keywords: Salmo salar ; exchange area ; secondary lamellae ; fish ; gas exchange ; respiratory system ; functional morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We show that many of the morphological features of the respiratory system of growth enhanced transgenic salmon are greater than those of similarly sized control salmon. Growth hormone transgenic Atlantic salmon, Salmo salar were the F2 generation produced using eggs from a transgenic F1 female and milt from a nontransgenic male. At the time the gill tissues were sampled, the transgenic salmon were growing 2.1 times more rapidly than the nontransgenic control salmon, and they had oxygen uptake rates that were about 1.6 times greater than control salmon. In the present study we show that the gill surface area available for respiratory exchange in the transgenic salmon is about 1.24 times that in control salmon which does not parallel the 1.6 elevation in oxygen uptake. The increase in gill exchange area was due largely to a relatively uniform increase in length of each gill filament.
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    URL: http://dx.doi.org/10.1023/A:1007574308129
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    Influence of Light Preferences on the Avoidance Responses of Lake Whitefish, Coregonus clupeaformis, to Cadmium (1999)
    Springer
    Environmental biology of fishes 55 (1999), S. 295-306 
    Details
    ISSN: 1573-5133
    Keywords: fish ; behaviour ; contaminant ; salmonid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The avoidance responses of lake whitefish to cadmium were studied in a counter-current trough where Cd was added to a shaded area to which whitefish were strongly attracted. In the first experiment, responses of individual fish to sequentially increasing Cd concentrations were monitored over a 1.6 h period. Whitefish did not start to move out of the shaded, Cd-treated side until a concentration of 125 µg l-1 was reached, and did not abandon this side except at the highest test concentration (250 µg l-1). This was 50 times the concentration at which whitefish avoided Cd (5 µg l-1) under uniform light conditions. In a second experiment, responses to a single high Cd concentration (150 µg l-1) were monitored over a 18.5 h period (4.5 h light:12 h dark:2 h light) in the same shaded test arena and Cd exposure conditions as above. During the initial light period Cd was avoided to the same degree as that observed at the same concentration in the first experiment, i.e. while some Cd avoidance was evident, fish remained attracted to the shaded, but Cd-treated side; this avoidance remained consistent until darkness (4.5 h). Once the light gradient was replaced with uniform darkness, avoidance of Cd became very strong, surpassing that observed under uniform lighted conditions. However, this response was transitory; after 10 h, Cd avoidance under total darkness returned to levels near those observed under daylight conditions with no light gradient present. Once the lights came back on (light gradient reestablished), fish were again attracted to the shaded side, and avoidance of Cd diminished, returning to the same level as that observed at the start of exposure. The above results demonstrate that when whitefish encounter competing gradients of Cd and light, attraction to favourable light conditions can strongly suppress avoidance of toxic concentrations of Cd, even over an extended period.
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    URL: http://dx.doi.org/10.1023/A:1007599520324
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    Black Male Bellies and Red Female Throats: Color Changes with Breeding Status in a Threespine Stickleback (1999)
    Springer
    Environmental biology of fishes 55 (1999), S. 237-244 
    Details
    ISSN: 1573-5133
    Keywords: black nuptial coloration ; female coloration ; Gasterosteus aculeatus ; parental success ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper provides the first report of black nuptial coloration on the ventral side for a population of threespine sticklebacks, Gasterosteus aculeatus, in Northern California. Black nuptial coloration was least intense during precourtship. Although the black coloration intensified during courtship, it was not a significant predictor of female choice and, unlike the red throat and blue eyes, was not inversely correlated with the number of female introductions necessary before spawning occurred. Black coloration was the most intense for males who successfully hatched embryos, supporting a parental-defense role late in the cycle. Unsuccessful fathers had more intensely colored red throats, blue eyes, and black bellies during most of the reproductive cycle than successful fathers. Some females in this study developed red coloration on their throat, although none to the intensity or distribution typical of a breeding male.
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    URL: http://dx.doi.org/10.1023/A:1007572620424
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    The status and distribution of lake sturgeon, Acipenser fulvescens, in the Canadian provinces of Manitoba, Ontario and Quebec: a genetic perspective (1997)
    Springer
    Environmental biology of fishes 48 (1997), S. 299-309 
    Details
    ISSN: 1573-5133
    Keywords: postglacial recolonization ; anthropogenic influences ; fish ; Acipenseridae ; conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Genetic analysis of mitochondrial DNA sequence variation indicates that most of a sample of 396 lake sturgeon, Acipenser fulvescens, from the northern part of their range belonged to either one of two haplotypes. The vast majority of fish from the Great Lakes/St. Lawrence and Mississippi drainages were of a single haplotype while those from the Hudson/James Bay were composed of both haplotypes. This haplotypic distribution suggests that fish from one refugium (possibly Missourian) recolonized the Hudson-James Bay drainage while those from a second (possibly Mississippian) recolonized the Laurentian Great Lakes and St. Lawrence River. Lake sturgeon still inhabit much of their native postglacial distribution in Manitoba, Ontario and Quebec. However, the stresses of commercial overexploitation and habitat alteration, usually through hydroelectric dam construction and operation, have either singly or in tandem brought about the reduction, if not extirpation, of some populations within the range. The largest zone of extirpation and population reduction has occurred in the Lake Winnipeg drainage area, which covers more than one-third of Manitoba. Other areas where populations have been reduced to remnant levels, if not extirpated, include the lower Laurentian Great Lakes of Lake Ontario and Lake Erie. In northern Ontario, lake sturgeon populations whose riverine habitats have been fragmented by two or more dams are substantially reduced from their former levels. In Quebec, more attention has been paid to limiting the exploitive stresses on lake sturgeon populations. Combination of the genetic and status data suggests that both northern and southern populations of lake sturgeon (possibly from two glacial refugia) have been impacted severely from anthropogenic influences.
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    URL: http://dx.doi.org/10.1023/A:1007367818353
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    Plasma concentrations of steroid hormones in male yellow perch, Perca flavescens: the effect of age and photothermal manipulation (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 97-105 
    Details
    ISSN: 1573-5133
    Keywords: fish ; 11-ketotestosterone ; testosterone ; estradiol ; sperm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plasma steroid concentrations in two and three year-old male yellow perch maintained under two different photothermal regimes were investigated. Initially, all fish kept indoors were exposed to the same water temperature (22 °C) and photoperiod (15L:9D). By the end of August, following the first sampling, fish were exposed to different photothermal regimes. Groups A2 (2 year old) and A3 (3 year old) were maintained under photothermal conditions similar to those of southern Ohio. Groups B2 (2 year old) and B3 (3 year old) were exposed to a condensed light/temperature regime designed to accelerate maturation. Testosterone (T) was the major circulating androgen in all groups. In regime A fish, plasma concentrations of 11-ketotestosterone (11KT) and T were very low in August, increased in October and remained elevated until March. In regime B plasma androgens were high until February and then dropped abruptly in March. The elevated circulating levels of 11KT and T were associated with production of sperm. The highest sperm concentration in the groups A3 and B3 was observed in February and December, respectively. There were no major differences in profiles and levels of plasma steroids between two age categories within each photothermal regime. These data indicate that the compression of the photothermal cycle accelerated both the occurrence of the low postspawning levels of circulating steroids and the completion of milt production. Higher sperm concentration observed in B3 group earlier in the season compared to A3 group also support the notion that the condensed photothermal cycle accelerated gonadal maturation. It appears that modification of the environmental cues may be a useful tool for manipulation of reproductive processes in male yellow perch.
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    URL: http://dx.doi.org/10.1023/A:1007460630535
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    Arrival of an Australian anguillid eel in New Zealand: an example of transoceanic dispersal (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 1-6 
    Details
    ISSN: 1573-5133
    Keywords: biogeography ; Anguilla ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Anguilla reinhardtii, hitherto known from eastern Australia, New Caledonia, Norfolk Island, and Lord Howe Island, has recently been discovered in rivers of northern New Zealand. Identification, based on morphological and genetic characteristics, is unequivocal; eight consecutive year classes have been found. The only reasonable explanation of this occurrence is transoceanic dispersal to New Zealand, probably from subtropical oceanic spawning grounds north of New Zealand. This corroborates past hypotheses that the strongly diadromous freshwater fish fauna of New Zealand is derived by transoceanic dispersal of known marine life intervals.
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    URL: http://dx.doi.org/10.1023/A:1007326405148
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    Factors influencing otolith strontium/calcium ratios in Anguilla japonica elvers (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 299-303 
    Details
    ISSN: 1573-5133
    Keywords: eel ; salinity ; temperature ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of temperature and salinity on the concentration ratios of strontium (Sr) to calcium (Ca) within the sagittal otoliths of elvers of the Japanese eel, Anguilla japonica, were studied by spot analysis using a wavelength dispersive X-ray electron microprobe. A total of 340 elvers were used: 100 elvers were reared for 15 days under various salinity conditions (freshwater, one-third seawater, two-thirds seawater and pure seawater at 22 °C; 240 elvers were reared for 58 days under various water temperature conditions (12, 17, 22, 27 °C) in either freshwater or pure seawater. Otolith Sr/Ca ratios were found to be positively correlated with water salinity. On the other hand, the Sr/Ca ratios were not found to be significantly different among the various temperature groups. The above results strongly suggest that the physiological mechanism of incorporation of Sr and Ca within the otolith of an eurythermal fish, Japanese eel, does not change within this range of temperatures (12–27 °C).
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    URL: http://dx.doi.org/10.1023/A:1007415420540
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    Effects of thermal regime on energy and nitrogen budgets of an early juvenile Arctic charr, Salvelinus alpinus, from Lake Inari (1999)
    Springer
    Environmental biology of fishes 54 (1999), S. 219-227 
    Details
    ISSN: 1573-5133
    Keywords: temperature ; energy partitioning ; nitrogen balance ; salmonid ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feed intake, growth, oxygen consumption and ammonia excretion of juvenile Arctic charr were measured over period of four weeks at different temperatures which were either constant (11.0, 14.4, 17.7 °C) or fluctuated daily (14.3 ± 1 °C). Maximum feed intake was estimated to occur at 14.3 °C, while oxygen consumption and nitrogen excretion were highest at the highest temperature, and growth rate was estimated to be highest at 13.9 °C. Feed conversion efficiency was estimated to be highest at 13.2 °C, where over 62.7% of ingested energy was allocated to growth. Metabolic rate accounted for 16–30% of ingested energy and nitrogen excretion was under 3% of ingested energy. The nitrogen budget was under similar thermal influences to the energy budget. Thermal fluctuation increased metabolic rate, but not feed intake, leading to a reduction in feed conversion efficiency under fluctuating temperature conditions.
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    URL: http://dx.doi.org/10.1023/A:1007566806749
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    Effects of Body Size and Food Ration on Over-winter Survival and Growth of Age-0 Atlantic cod, Gadus morhua (1999)
    Springer
    Environmental biology of fishes 54 (1999), S. 413-420 
    Details
    ISSN: 1573-5133
    Keywords: mortality ; specific growth rate ; Newfoundland ; fish ; aquaculture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examined the effects of body size and food ration on over-winter survival of age-0 Atlantic cod. Cod were divided into two groups based on standard length (large=76.95±1.10 mm SL; small=57.65±1.02 mm SL; mean±1 SE) and wet weight (large=4.02± 0.21 g; small=1.52±0.09 g). Replicate tanks (n=2) of 10 large and 10 small cod were exposed to one of two food rations (0.25% and 1.0% body weight day-1) for the entire experiment (December to June). Tanks were examined daily for mortalities and feeding was adjusted accordingly. The experiment was run under ambient light and seawater conditions. All but large age-0 cod exposed to the low food ration grew over the course of the experiment. The specific growth rate (SGR) of small cod was significantly higher (0.2425% wet weight day-1) than that of the large fish (0.0443% wet weight day-1). Food ration had no significant influence on SGR or over-winter survival. Significantly more of the large age-0 cod survived the winter (58.5% of those originally introduced) compared to the smaller fish (14%). Our results are consistent with those from studies of several other fish species, and are discussed in relation to the ecology of age-0 cod, and their potential use in aquaculture in Newfoundland.
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    URL: http://dx.doi.org/10.1023/A:1007587101669
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    Accumulation of mercury in estuarine food chains (1998)
    Springer
    Biogeochemistry 40 (1998), S. 235-247 
    Details
    ISSN: 1573-515X
    Keywords: fish ; invertebrates ; ligands ; mercury ; methylmercury ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract To understand the accumulation of inorganic mercury and methylmercury at the base of the estuarine food chain, phytoplankton (Thalassiosira weissflogii) uptake and mercury speciation experiments were conducted. Complexation of methylmercury as methylmercury-bisulfide decreased the phytoplankton uptake rate while the uptake rate of the methylmercury-cysteine and -thiourea complexes increased with increasing complexation by these ligands. Furthermore, our results indicated that while different ligands influenced inorganic mercury/methylmercury uptake by phytoplankton cells, the ligand complex had no major influence on either where the mercury was sequestered within the phytoplankton cell nor the assimilation efficiency of the mercury by copepods. The assimilation efficiency of inorganic mercury/methylmercury by copepods and amphipods feeding on algal cells was compared and both organisms assimilated methylmercury much more efficiently; the relative assimilation efficiency of methylmercury to inorganic mercury was 2.0 for copepods and 2.8 for amphipods. The relative assimilation is somewhat concentration dependent as experiments showed that as exposure concentration increased, a greater percentage of methylmercury was found in the cytoplasm of phytoplankton cells, resulting in a higher concentration in the copepods feeding on these cells. Additionally, food quality influenced assimilation by invertebrates. During decay of a T. weissflogii culture, which served as food for the invertebrates, copepods were increasingly less able to assimilate the methylmercury from the food, while even at advanced stages of decay, amphipods were able to assimilate mercury from their food to a high degree. Finally, fish feeding on copepods assimilated methylmercury more efficiently than inorganic mercury owing to the larger fraction of methylmercury found in the soft tissues of the copepods.
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    URL: http://dx.doi.org/10.1023/A:1005959211768
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    Development of community metrics to evaluate recovery of Minnesota wetlands (1998)
    Springer
    Journal of aquatic ecosystem stress and recovery 6 (1998), S. 217-234 
    Details
    ISSN: 1573-5141
    Keywords: wetlands ; land use ; biological integrity ; biological diversity ; ecosystem monitoring ; ecosystem recovery ; amphibians ; fish ; birds ; plants ; invertebrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monitoring wetland recovery requires assessment tools that efficiently and reliably discern ecosystem changes in response to changes in land use. The biological indicator approach pioneered for rivers and streams that uses changes in species assemblages to interpret degradation levels may be a promising monitoring approach for wetlands. We explored how well metrics based on species assemblages related to land use patterns for eight kinds of wetlands in Minnesota. We evaluated land use on site and within 500 m,1000 m, 2500 m and 5000 m of riverine, littoral, and depressional wetlands (n = 116) in three ecoregions. Proportion of agriculture, urban, grassland, forest,and water were correlated with metrics developed from plant, bird, fish, invertebrate, and amphibian community data collected from field surveys. We found79 metrics that relate to land use, including five that may be useful for many wetlands: proportion of wetland birds, wetland bird richness, proportion of insectivorous birds, importance of Carex, importance of invasive perennials. Since very few metrics were significant for even one-half of the wetland types surveyed, our data suggest that monitoring recovery in wetlands with community indicators will likely require different metrics,depending on type and ecoregion. In addition, wetlands within extensively degraded ecoregions may be most problematic for indicator development because biotic degradation is historic and severe.
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    Seasonal variation of muscle metabolic organization in rainbow trout (Oncorhynchus mykiss) (1997)
    Springer
    Fish physiology and biochemistry 16 (1997), S. 139-155 
    Details
    ISSN: 1573-5168
    Keywords: season ; metabolic organization ; muscle ; fish ; temperature ; lipid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examined how muscle metabolic organization varied during an annual cycle in which rainbow trout (Oncorhynchus mykiss) were held in outdoor holding ponds in which they were exposed to natural changes in temperature (range 0.2 to 15.6°C) and photoperiod. We examined the activities of glycolytic and mitochondrial enzymes in red and white muscle to evaluate whether trout enhance their capacity for lipid and carbohydrate oxidation during cold-acclimization. When assayed at habitat temperature, the enzyme activities generally increased in spring to reach a maximum in summer followed by a decrease in the fall. This led to significantly higher activities at warm than cold periods for all enzymes measured in red muscle and all but one in white muscle. The activities at 10°C provided little evidence for compensatory adjustments of aerobic capacity. Particularly in red muscle, enzyme levels at 10°C were generally lower during cold than warm periods. The variation of enzyme activities throughout the cycle was not due to changes in protein concentration, as the same responses were observed when activities were expressed per g wet mass or per mg protein. Although the aerobic capacity did not increase with cold-acclimatization, the relative capacity for lipid oxidation was higher in winter than in summer trout. In contrast, the relative capacity for aerobic glycolysis was higher in summer than in winter trout. Thus, the metabolic capacities of trout muscle undergo seasonal reorganization.
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    URL: http://dx.doi.org/10.1007/BF00004671
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    Plasticity of the properties of mitochondria from rainbow trout red muscle with seasonal acclimatization (1997)
    Springer
    Fish physiology and biochemistry 16 (1997), S. 531-541 
    Details
    ISSN: 1573-5168
    Keywords: mitochondria ; muscle ; thermal acclimatization ; fish ; substrate preferences ; phospholipid fatty acid composition ; oxidative capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cold-acclimation of rainbow trout brings only limited changes in muscle metabolic capacities, but marked modifications in membrane composition. Thus, we examined whether the functional properties of mitochondria from trout red muscle were modified by seasonal temperature acclimatization. Mitochondria from fall-acclimatized trout had higher maximal capacities (state 3 rates) for the oxidation of pyruvate and acyl carnitines at 12 and 20 °C than mitochondria isolated from summer-acclimatized trout. For these substrates, the increased oxidative capacity completely compensated for the seasonal drop in temperature. Pyruvate and palmitoyl carnitine were consistently the preferred substrates, while decanoyl and octanoyl carnitine were oxidized at higher rates than glutamine, particularly in fall trout. State 4 rates of oxygen uptake (obtained when all ADP has been converted to ATP) differed less among substrates, but varied seasonally. State 4 rates at 12 and 20 °C were higher in mitochondria isolated from fall than summer trout. At low temperatures, the Q10 of both maximal and state 4 rates of substrate oxidation tended to be higher for mitochondria from fall trout. The apparent Arrhenius activation energy (Ea) for mitochondrial pyruvate oxidation was higher in fall than summer trout whereas the Ea’s for palmitoyl carnitine and decanoyl carnitine oxidation did not change. The fatty acids of mitochondrial phospholipids from fall trout were more polyunsaturated than those from summer trout, with 12% more double bonds occurring than in summer trout, suggesting that membrane restructuring may be involved in the observed compensatory responses.
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    Reproduction related immunoglobulin changes in rainbow trout (1997)
    Springer
    Fish physiology and biochemistry 17 (1997), S. 415-421 
    Details
    ISSN: 1573-5168
    Keywords: fish ; trout ; reproduction ; seasonal changes ; immunoglobulin ; testosterone ; estradiol-17β ; 11-ketotestosterone ; water temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Annual changes in plasma immunoglobulin (IgM) levels were investigated in three strains of rainbow trout Oncorhynchus mykiss which have different spawning periods, i.e., September–October, November–December, and January, reared under constant water temperature and natural day length. Plasma IgM levels decreased during the spawning season in all strains tested. The IgM changes became reversed in response to significant increases in plasma testosterone (T) and estradiol-17β in females and T and 11-ketotestosterone in males. Though the IgM decline showed a connection with suppressed immunocompetence, since many mature fish caught fungal diseases, no clear differences were observed in the plasma IgM levels between infected and noninfected fish during the spawning season. Incidentally, plasma IgM levels in infection prone fish were higher than in noninfection prone fish prior to the spawning season, whereas coincident differences in the plasma steroid levels were observed. Immature fish reared under lower water temperatures showed lower IgM levels. The effect of water temperature may have to be considered when analyzing the defense mechanism during the spawning season in rainbow trout.
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    URL: http://dx.doi.org/10.1023/A:1007795827112
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    Gonadotropin-releasing hormone and gonadotropin in goldfish and masu salmon (1997)
    Springer
    Fish physiology and biochemistry 17 (1997), S. 1-8 
    Details
    ISSN: 1573-5168
    Keywords: gonadotropin-releasing hormone ; GnRH ; gonadotropin ; GTH ; reproduction ; reproductive endocrinology ; gonadal development ; fish ; goldfish ; masu salmon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproductive activities in vertebrates are regulated by an endocrine system, consisting of the brain-pituitary-gonad axis. In teleosts, gonadotropin-releasing hormone (GnRH) in the brain stimulates gonadotropin (GTH) release in the pituitary gland, but because of lack of the portal vessel, it is not known when and how much GnRH is released for the regulation of GTH release. There are multiple molecular types of GnRH in teleosts and several distinct populations of GnRH neurons in the brain. However, we do not know which types and populations of GnRH neurons regulate reproductive activities. Here we summarize our recent studies on GnRH and GTH in masu salmon Oncorhynchus masou and goldfish Carassius auratus. Immunocytochemistry showed the location and molecular types of GnRH neurons. Salmon (sGnRH) and chicken-II GnRH (cGnRH-II) neuronal fibers were widely distributed in the brain of both masu salmon and goldfish. Only sGnRH fibers were observed in the pituitary of masu salmon, whereas both sGnRH and cGnRH-II fibers were observed in the goldfish pituitary, indicating that species specific GnRH profiles are involved in the regulation of pituitary function in teleosts. A series of experiments in masu salmon and goldfish suggest that among GnRH neuron populations GnRH neurons in the ventral telencephalon and the hypothalamus regulate GTH release, and that GnRH of the terminal nerve origin is not essential to gonadal maturation and ovulation. The biological function of other GnRH neurons remains unkown. Two GTHs appear to be characteristic of teleost; however, regulation of reproduction by these GTHs is a question that remains to be elucidated. In salmonid species, it is proposed that GTH I stimulates early gonadal development, whereas GTH II acts in later stages. When GTH expression was examined in goldfish, both GTH I β and II β mRNA levels in the pituitary gland showed increases in accordance with gonadal development, unlike the sequential expression of GTH subunits in salmonids. The expression of these GTH subunit mRNAs were affected by water temperature, starvation, and steroid hormones in goldfish, but in what manner these two GTHs regulate gonadal development remains to be clarified.
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    Vascular actions of neurohypophysial peptides in the flounder (1997)
    Springer
    Fish physiology and biochemistry 17 (1997), S. 313-318 
    Details
    ISSN: 1573-5168
    Keywords: teleost ; fish ; blood pressure ; arginine vasotocin ; isotocin ; ventral aorta ; dorsal aorta ; neurohypophysial hormone receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Free swimming, chronically cannulated flounder have been used to study the blood pressure effects of arginine vasotocin (AVT) and isotocin. The initial fall in dorsal aortic blood pressure following AVT injection coincided with an increase in ventral aortic blood pressure, suggesting AVT caused constriction of the arterio-arterial pathway. Ventral aortic blood pressure increased in a dose dependent manner with increasing AVT dose. Dorsal aortic blood pressure also increased following the initial fall but not in a dose dependent manner, the effect at higher doses being off set by branchial vasoconstriction. Isotocin also caused dorsal aortic blood pressure to fall due to branchial vasoconstriction, but no subsequent pressor effect was seen. Branchial vasoconstriction caused by both teleost neurohypophysial peptides suggests the presence of neurohypophysial peptide receptor(s) in the gill, although it is unclear as to whether this is a single common receptor or different populations for each peptide. The dorsal aortic pressor effect of AVT and its absence following isotocin injection suggests there may be other types of neurohypophysial receptors in post-branchial vascular beds. The vascular actions of AVT and isotocin suggest that these peptides may play some role in the regulation of blood pressure or regional blood flow distribution.
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    URL: http://dx.doi.org/10.1023/A:1007745821969
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    The determination of lipase and phospholipase activities in gut contents of turbot (Scophthalmus maximus) by fluorescence-based assays (1998)
    Springer
    Fish physiology and biochemistry 19 (1998), S. 153-162 
    Details
    ISSN: 1573-5168
    Keywords: lipid digestion ; lipases ; phospholipases ; esterases ; fish ; fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To study the potential of fluorescence based assays in the study of lipid digestion in fish, acyl esters of 4-methylumbelliferone and 1-acyl-2-[6 (7 nitro-1,3 benzoxadiazol-4-yl)amino]caproyl labeled phosphatidylcholine compounds (NBD-PC) were used as substrates for the assay of neutral lipase and phospholipase, respectively, in the gut contents of turbot. 4-Methylumbelliferyl hepatanoate (4-MUH) was hydrolysed at a higher rate than the butyrate or oleate esters whilst the hexanoic (C6) ester of NBD-PC was a more convenient substrate for the phospholipase assay than the dodecanoic (C12) ester. Neutral lipase activity was almost 10% higher when 50 mm potassium phosphate buffer pH 7.8 was used instead of 0.01 m citrate/sodium phosphate buffer pH 7.2. Both assays were very sensitive: neutral lipase and phospholipase activities were detectable at a minimum protein concentration in the digesta of 0.04 and 1.25 mg/ml, respectively. When the variations in lipolytic activities with gut segment and with size of fish were examined neutral lipase activity was always found to be higher in the hindgut and rectum segments than in the foregut. Although phospholipase activity was also found to be highest in the hindgut of the largest fish examined (av. wt. 182.3g), in fish of average weight 8g fish the activity was similar in all three segments. In the digesta from the whole gut of smaller fish (av. wt. 0.2, 0.6 and 1.43g) neutral lipase and phospholipase activities increased with increasing body mass when expressed as per ml of digesta. It is concluded that fluorescence-based assays are applicable to the study of lipid digestion in fish of different size.
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    URL: http://dx.doi.org/10.1023/A:1007734425931
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    Cellular distribution of insulin-like growth factor II (IGF-II) mRNA and hormonal regulation of IGF-I and IGF-II mRNA expression in rainbow trout testis (Oncorhynchus mykiss) (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 219-229 
    Details
    ISSN: 1573-5168
    Keywords: fish ; gene expression ; GH ; GtH ; gonad ; growth factors ; RT-PCR ; salmonid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this study, Northern blot analysis of RNA from trout testis revealed a single transcript of insulin-like growth factor II (IGF-II) around 4.7 kb. The cellular distribution of IGF-II mRNA was studied and quantified in different testicular cells enriched populations by RT-PCR. IGF-II mRNA appears to be expressed in all cellular types tested: spermatogonia A and B, primary spermatocytes, spermatids and secondary spermatocytes and Sertoli cells. A significantly higher expression of IGF-II was found in premeiotic germ cells. The levels of IGF-II mRNA appear to be higher than those of IGF-I in immature trout testis, as judged from the semi-quantitative RT-PCR results. These data suggest that in addition to IGF-I, IGF-II may play a role in testicular physiology in fish. The hormonal regulation of IGF-I and IGF-II gene expression was investigated both in vitro and in vivo using RT-PCR approach. Gonadotropin (GtH) added to testicular explants increased IGF-II mRNA levels but had no effect on IGF-I. No statistically significant effect was observed with androgens. In vivo, GH and pituitary extracts resulted in an 8 fold and 2-3 fold increase in both IGF-I and IGF-II mRNA levels, respectively. Taken together, our study suggests that IGF-I and IGF-II may act as local mediators of GH and GtHs in fish testis. Moreover, our results imply that in fish testicular cells, IGFs are potential paracrine/autocrine regulators inside the spermatogenic compartment and can act directly on germ cells to stimulate their proliferation.
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    URL: http://dx.doi.org/10.1023/A:1007735314871
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    Do digestive enzymes set a physiological limit on growth rate and food conversion efficiency in the Atlantic cod (Gadus morhua)? (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 293-303 
    Details
    ISSN: 1573-5168
    Keywords: acid proteases ; alkaline phosphatase ; chymotrypsin ; digestive enzymes ; fish ; food intake ; glutamyltransferase ; growth hormone ; protein content ; trypsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objective of this study was to determine the potential sites of maximal growth limitation in Atlantic cod (Gadus morhua). Forty cod were reared in ten sea water tanks. Fish were randomly divided into 5 groups, a control group (injected with saline solution) and 4 experimental groups that received different levels of recombinant bovine somatotropin (rbST: 1.0, 2.0, 4.0 and 10.0 μg g fish−1 2 weeks−1) by injection in the abdominal cavity. Fish were fed ad libitum 3 times a week during four weeks. We measured individual body mass, growth rate, food intake and food conversion efficiency. At the end of the experiment, we measured the activity of acid proteases in the stomach; trypsin and chymotrypsin in the pyloric caeca; alkaline phosphatase (ALP) and glutamyltransferase (GGT) in the intestine. No significant differences were observed in growth rate, food intake or food conversion efficiency among the five groups. Trypsin, chymotrypsin, ALP and GGT activities when expressed in U g fish−1 were correlated with growth rate. These enzymes were also correlated with food ingestion except for trypsin when expressed in U mg protein−1. Trypsin was the only enzyme that showed a significant correlation with food conversion efficiency. Our conclusion is that, at the level of digestion, trypsin is the only enzyme measured that could be suspected to potentially limit growth rate in cod.
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    URL: http://dx.doi.org/10.1023/A:1007791019523
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    Alloparental care in fishes (1999)
    Springer
    Reviews in fish biology and fisheries 9 (1999), S. 45-70 
    Details
    ISSN: 1573-5184
    Keywords: adoption ; alloparental care ; brood parasitism ; fish ; mutualism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Alloparental care, care directed at non-descendant young, presents a potential challenge to evolutionary ecologists because investment in non-descendant eggs and young gives the appearance of maladaptive behaviour. Yet wherever there is parental care in fishes, there is usually alloparental care. As such, alloparental care is an integral part of care in fishes. Alloparental care appears to have arisen independently many times in disparate taxa. The chief reason for this is the low cost of care, relative to homeotherms, both in terms of low post-zygotic investment to nourish young, and low risk of predation to the parent during brood defence. In some cases, alloparenting is misdirected parental care and maladaptive. A celebrated example of brood parasitism in fish is that of the catfish Synodontis multipunctatus, which parasitizes broods of mouthbrooding cichlids. Previously unpublished data on the reproductive biology of S. multipunctatus are reported here. However, in the majority of cases, particularly for the widespread phenomena of zygote dumping (nest associates) in the Cyprinidae and adoption of non-descendant free-swimming young in brood-guarding Cichlidae, alloparental care is a mutualistic relationship maintained by natural selection. This review describes broad patterns of known examples of alloparental care, the pathways to adoption, and highlights the ways in which alloparents derive fitness benefits. By caring for non-descendant young, an alloparent may benefit by one or more of the following phenomena: acquisition of mates, confusion effect, dilution effect, selfish herd effect, selfish shepherd effect, kin selection, and reciprocal altruism. Although the breadth and diversity of examples of alloparental care in fishes is growing, to date, these accounts have been largely descriptive. Future research should be directed at careful documentation of the fitness consequences for both donor and alloparent. These are the data that are needed to fully understand the evolutionary underpinnings of alloparental care, and by extension, parental care.
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    URL: http://dx.doi.org/10.1023/A:1008865801329
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    Molecular markers and the species concept: New techniques to resolve old disputes? (1999)
    Springer
    Reviews in fish biology and fisheries 9 (1999), S. 379-382 
    Details
    ISSN: 1573-5184
    Keywords: fish ; molecular marker ; speciation ; species concept
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    URL: http://dx.doi.org/10.1023/A:1008967532146
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    How light, a predator, and experience influence bluegill use of shade and schooling (1997)
    Springer
    Environmental biology of fishes 49 (1997), S. 79-87 
    Details
    ISSN: 1573-5133
    Keywords: behavior ; predator‐prey interaction ; shade ; schooling ; largemouth bass ; fish ; Lepomis macrochirus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bluegills, Lepomis macrochirus, form schools and use shade to avoid predators. How light intensity, predators, and experience might affect antipredator behavior of bluegill are not well understood. Hence, we evaluated use of shade and schooling by naive (hatchery) and experienced (wild) bluegills (50–60 mm total length) at four light levels (1.5, 85, 169, 340 lux) in the presence and absence of a model predator in experimental pools. Naive bluegills used shade extensively at all light levels, even when the predator was in the shade. They rarely schooled, preferring to shoal in the shade. Experienced bluegill used shade when the predator was in the open and avoided shade when the predator was there. Schooling was more prevalent at low light levels when shade was less intense. Use of shade became an increasingly important behavior at higher light levels, unless the predator was in the shade. A shaded predator caused experienced bluegills to shoal tightly in the opposite, open area. These data suggest naive bluegills may not have considered the model predator a threat. Their behavior suggests avian predator avoidance, a possibility given that avian predators were present at the hatchery. Experienced bluegill employed behaviors that would be useful in avoiding piscine predators.
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    URL: http://dx.doi.org/10.1023/A:1007353314602
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    Critical thermal maxima of diploid and triploid brook charr, Salvelinus fontinalis (1997)
    Springer
    Environmental biology of fishes 49 (1997), S. 259-264 
    Details
    ISSN: 1573-5133
    Keywords: triploidy ; thermal tolerance ; lethal limits ; brook trout ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The purpose of this experiment was to determine whether diploid and triploid brook charr, Salvelinus fontinalis, differ in their critical thermal maxima (CTM). Two age classes were tested (underyearlings, having average weight of 25 g, and yearlings, having average weight of 668 g) at two rates of temperature increase (2° C h-1 and 15° C h-1). No effect of ploidy on CTM was found. Fish exposed to the faster rate of temperature increase had higher CTM values than those exposed to the slower rate (underyearlings: 29.5 ± 0.1° C versus 29.1 ± 0.1° C in one trial and 29.8 ± 0.1° C versus 28.3 ± 0.1° C in a second trial; yearlings: 29.3 ± 0.1° C versus 27.7 ± 0.1° C in two trials, p 〈 0.001 in all cases). Underyearlings had higher CTM values than yearlings (29.2 ± 0.1° C versus 28.5 ± 0.1° C, p 〈 0.05). Female yearlings, which were immature, had higher CTM values than males, which had previously matured as one-year-olds (28.8 ± 0.1° C versus 28.3 ± 0.1° C, p 〈 0.001).
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    URL: http://dx.doi.org/10.1023/A:1007361231325
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    A modified decalcification technique for enhancing growth bands in deep-coned vertebrae of elasmobranchs (1997)
    Springer
    Environmental biology of fishes 50 (1997), S. 225-230 
    Details
    ISSN: 1573-5133
    Keywords: Galeus melastomus ; blackmouth catshark ; nitric acid ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A technique for enhancing growth bands on vertebrae was assayed using 477 centra from blackmouth catsharks, Galeus melastomus. Specimens were caught at depths between 200 and 800 meters off the southern Portuguese coast (Algarve) during an IPIMAR research cruise in August 1994. Total lengths ranged from 12 to 71 cm. Standard vertebral ageing techniques, such as silver nitrate impregnation, haematoxylin staining, grinding and shading failed to produce clearly contrasting bands. A method solely based on vertebra decalcification with nitric acid (5%) yielded the most satisfactory results. This technique provided clear band differentiation and was used by two independent readers. The analysis of differences in band counts between readers was based on: percent of disagreements, percent of disagreement by length group, index of average percent error and Wilcoxon's signed ranks test. The majority of differences corresponded to only one band of disagreement and disagreements have been found to increase with length, which stresses the need for a larger sampling effort on the larger and older individuals. The index of average percent error was estimated as 4.6% and no statistical differences were detected between readers' results.
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    URL: http://dx.doi.org/10.1023/A:1007368025164
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    Feeding ecology and interannual variations in diet of southern bluefin tuna, Thunnus maccoyii, in relation to coastal and oceanic waters off eastern Tasmania, Australia (1997)
    Springer
    Environmental biology of fishes 50 (1997), S. 275-291 
    Details
    ISSN: 1573-5133
    Keywords: fronts ; shelf ; oceanography ; scombrid ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diets of 1219 southern bluefin tuna, Thunnus maccoyii, from inshore (shelf) and offshore (oceanic) waters off eastern Tasmania were examined between 1992 and 1994. Immature fish (〈 155 cm fork length) made up 88% of those examined. In all, 92 prey taxa were identified. Inshore, the main prey were fish (Trachurus declivis and Emmelichthys nitidus) and juvenile squid (Nototodarus gouldi). Offshore, the diversity was greater, reflecting the diversity of micronekton in these waters. Interestingly, macrozooplankton prey (e.g. Phronima sedentaria) were prevalent in tuna 〉 150 cm. The offshore tuna, when in subantarctic waters, ate relatively more squid than when in the East Australia Current. In the latter, fish and crustacea were more important, although there were variations between years. No relationship was found between either prey type or size with size of tuna. Feeding was significantly higher in the morning than at other times of the day. The mean weight of prey was significantly higher in inshore-caught tuna than in those caught offshore. We estimated that the mean daily ration of southern bluefin tuna off eastern Tasmania was 0.97% of wet body weight day−1. However, the daily ration of inshore-caught tuna was ∼ 3 times higher (2.7%) than for tuna caught offshore (0.8%) indicating that feeding conditions on the shelf were better than those offshore. Our results indicate that the inshore waters of eastern Tasmania are an important feeding area for, at least, immature southern bluefin tuna.
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    URL: http://dx.doi.org/10.1023/A:1007326120380
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    Weight-length relationship and condition of the characiform Triportheus guentheri (1997)
    Springer
    Environmental biology of fishes 50 (1997), S. 319-330 
    Details
    ISSN: 1573-5133
    Keywords: condition factor ; biometric indices ; Brazil ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sources of variations in the weight-length relationship parameters, and in the Fulton's, allometric, and relative condition factors (K) of the characiform fish Triportheus guentheri were investigated. The use of these indices as indicators of condition were also discussed. The 2899 females and 2491 males were captured with gill nets from January 1986 to March 1988 in Três Marias Reservoir (18° 15′ and 45° 15′ W), Brazil. Weight-length relationship parameters varied monthly in both sexes mainly due to the skewness of the relative frequency of the number of fish per body length. This suggests that a selective sample and/or the population length structure may strongly influence the estimate of those parameters. The K showed high correlations (r ≥ 0.99) among themselves. Their variations were ascribed to carcass weight in both sexes when analyzed by month, or to the ovary weights when analyzed by female gonad development intervals. The monthly weight-length relationship parameters of T. guentheri presented low or null correlation with K, except for the female's coefficient of regression. Problems using these parameters as indicators of condition suggested that they are not good indices to express condition. Some restrictions regarding the use of K are discussed.
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    URL: http://dx.doi.org/10.1023/A:1007316028288
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    Predation of zebra mussels by round gobies, Neogobius melanostomus (1997)
    Springer
    Environmental biology of fishes 50 (1997), S. 267-273 
    Details
    ISSN: 1573-5133
    Keywords: exotic species ; laboratory experiment ; size selectivity ; Great Lakes ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Preliminary gut analysis of a recent Great Lakes invader, the round goby, Neogobius melanostomus (7.0–8.4 cm), collected from the Detroit River, showed that they ate zebra mussels (58%), snails (6%), and other invertebrates (36%), including aquatic insects (Hexagenia), softshelled crayfish, and zooplankton. Because zebra mussels, Dreissena polymorpha, predominated as prey, we investigated the ability of round gobies to consume different size classes of zebra mussels. In laboratory experiments, we examined feeding preferences of three size classes of round gobies (5.5–6.9 cm; 7.0–8.4 cm; 8.5–10.3 cm standard length) on four different size classes of zebra mussels (6.0–9.9 mm, 10.0–12.9 mm, 13.0–15.9 mm, 16.0–18.9 mm). All sizes of round gobies ate zebra mussels 〈 10.0 mm. Only the largest size class of round gobies ate larger zebra mussels (10.0–12.9 mm) when all prey sizes were presented. The association between the total mass of zebra mussels available and the amount consumed by round gobies increased positively up to about 6.5 g of available mussels and then levelled off. Round gobies consumed an average of 1.0 g of mussels in 24 h. There was a significant positive relationship between gape size and standard length of round gobies. Although larger round gobies (over the size range of fish in our study) are able to consume larger zebra mussels, small mussels were preferred. Our findings suggest that the preference of small zebra mussels by round gobies has the potential to alter the size structure of zebra mussel populations.
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    URL: http://dx.doi.org/10.1023/A:1007379220052
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    Effects of environmental hypoxia on oxygen consumption rate and swimming activity in juvenile white sturgeon, Acipenser transmontanus, in relation to temperature and life intervals (1997)
    Springer
    Environmental biology of fishes 50 (1997), S. 383-389 
    Details
    ISSN: 1573-5133
    Keywords: routine metabolic rate ; oxyconformer ; Acipenseridae ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Routine oxygen consumption rates (MO2) and swimming activity rates of juvenile white sturgeon were determined using closed respirometers at life-interval-appropriate temperatures: 10° C (0.2 g mean wet weight), 16° C (1.9 g mean wet weight), and 20° C (63.1 g mean wet weight) under normoxic (PO2 〉 140 mmHg) and moderately hypoxic (PO2=80 ± 5.0 mmHg) water conditions. At all temperatures and body sizes, hypoxia significantly depressed (p 〈 0.05) MO2 (57% mean reduction) and swimming activity (70% mean reduction). Overall mean MO2 was 228 µg O2 g-1 wet weight h-1 (normoxia) and 99 µg O2 g-1 wet weight h-1 (hypoxia). Thus, juvenile white sturgeon appear to decrease overall energy expenditures (hypometabolism) during hypoxia via reductions in spontaneous swimming activity. This is a life style that may increase survival during widespread or prolonged environmental hypoxia.
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    Temperature, growth and dietary effects on fish mercury dynamics in two Ontario lakes (1998)
    Springer
    Biogeochemistry 40 (1998), S. 175-187 
    Details
    ISSN: 1573-515X
    Keywords: bioenergetics ; fish ; mercury ; methylmercury ; models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A bioenergetics-based model was used to investigate the effects of temperature, growth and dietary exposure on methylmercury dynamics in walleye (Stizostedion vitreum) and yellow perch (Perca flavescens) from two lakes sampled in northwestern Ontario. Orange Lake was smaller, warmer, had slower fish growth and higher mercury concentrations in yearling yellow perch and walleye (three fold difference in 40 cm walleye) than Trout Lake. The model was applied to test the hypothesis that higher water temperatures in Orange Lake increased metabolic needs, food consumption and mercury uptake in fish. The effects of different growths rates in the lakes were also considered. Temperature/metabolic effects and growth effects on internal methylmercury dynamics in walleye and perch were predicted to occur but be of secondary importance. Different dietary exposure to methylmercury was likely the dominant source of variation in fish mercury concentrations between the two lakes.
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    URL: http://dx.doi.org/10.1023/A:1005986505407
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    Transfer of heavy metals from sediment to fish, and their biliary excretion (1995)
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    Journal of aquatic ecosystem stress and recovery 4 (1995), S. 221-230 
    Details
    ISSN: 1573-5141
    Keywords: bile ; Daphnia magna ; fish ; rainbow trout ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Uptake and biliary excretion of metals were studied in rainbow trout, Oncorhynchus mykiss, exposed through spiked sediment to a mixture of seven heavy metals. Metal concentrations and toxicity of bile and blood plasma were used as indicators of exposure. Among the seven metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) only three (Cu, Hg, and Pb) were concentrated in the bile (bile-plasma ratio 〉1). Bile-plasma ratios in the rainbow trout were similar to those found in rats for Cu and Hg. Daphnia magna bioassays were used to determine toxicity of bile and blood plasma in the same trout. Toxicity of bile and blood plasma increased after treatment with acid. An analysis of variance (ANOVA) showed that toxicity of bile and blood plasma to D. magna in metal-exposed trout was significantly correlated with (1) bile and blood plasma test concentration, (2) acid treatment of bile and blood plasma (hydrolysis of metal-plasma and metal-bile complexes) and (3) sediment concentration of metals during exposure of trout. In order to significantly detect the magnitude of the exposure to a xenobiotic the biomarker must respond in a dose- or time-dependent manner. Therefore, the potential use of bile toxicity as a biomarker of heavy metal exposure in fish is probably limited by the low bioconcentration of many of these toxicants in bile.
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    URL: http://dx.doi.org/10.1007/BF00118002
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    Relations between resuspension and the content of 137Cs in freshwater fish in some Swedish lakes (1995)
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    Journal of aquatic ecosystem stress and recovery 4 (1995), S. 285-294 
    Details
    ISSN: 1573-5141
    Keywords: 137Cs ; freshwater ; sediment traps ; resuspension ; sediment ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In many Swedish lakes, the fallout of 137Cs from the Chernobyl accident in April 1986 has largely accumulated in the sediments. The availability and transfer of deposited 137Cs to biota is influenced by factors such as resuspension. The frequency of resuspension and the 137Cs-content of different fish species was studied in three shallow lakes in Uppland, central Sweden, and in one deeper lake in northern Sweden. Resuspension was measured by the use of sediment traps. Sedimentation rates measured from the traps in the shallower lakes were 5–10 times higher than normal for this type of lake, indicating that resuspension was an important factor. The decrease of the 137Cs-content in muscle tissue of pike, perch and roach was slow in each of the shallow lakes. 137Cs decreased by about 30% over a period of 2 years in the shallowest lake (maximum depth 4 m), whereas 137Cs decreased by 50% in the deeper lakes (maximum depth 10 m). The slower rates of decline of 137Cs in biota from the shallow lakes, are probably a function of sediment dynamics (mainly influenced by lake morphometry, wind direction and strength). They may be influenced, also, by bioavailability of resuspended sediment material. In the deepest northern lake, much of the 137Cs-containing material collected in the sediment traps originated from the catchment area. Resuspension was minimal, and the high activity of 137Cs in the sediment had no effect on content or decline of 137Cs in lake fish.
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    URL: http://dx.doi.org/10.1007/BF00118009
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    Characterization of molecular variants of GnRH, induction of spermiation and sex reversal using salmon GnRH-A and domperidone in the protogynous diandric fish, Synbranchus marmoratus Bloch, (Teleostei, Synbranchidae) (1997)
    Springer
    Fish physiology and biochemistry 16 (1997), S. 425-436 
    Details
    ISSN: 1573-5168
    Keywords: fish ; GnRH ; domperidone ; hermaphroditism ; protogynous ; diandric ; sex reversal ; spermiation ; Synbranchidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper studies the molecular variants of gonadotropin-releasing hormone (GnRH) present in the brain of the protogynous swamp eel, Synbranchus marmoratus, and the effects of the administration of salmon GnRH analogue (sGnRH-A) and the dopamine receptor antagonist, domperidone (DOM) on final maturation and gamete release in this species. Evidence for the presence of two GnRH variants, sGnRH and cIIGnRH were obtained by reverse phase high-pressure liquid chromatography (RP-HPLC) and radioimmunoassay with different antisera. The effects of treatment with sGnRH-A+DOM were checked by three ways: oocyte and milt release by stripping, histological analysis of the gonadal tissue, and androgen serum levels at different times throughout the experiment. In males, spermiation was induced after three weeks of treatment. In the female group, sGnRH-A+DOM did not induce ovulation at the end of the experiment. Histological analysis of the gonads from the female group showed evidence of sex reversal. All the treated fish had elevated androgen serum levels from the third week, with respect to control fish. In all cases, serum estradiol levels were undetectable. These results suggest that treatment with sGnRH analog and DOM induce sex reversal in female and spermiation in males.
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    URL: http://dx.doi.org/10.1023/A:1007772416539
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    Turnover of α-, γ, and δtocopherol and distribution insubcellular and lipoprotein fractions indicate presence of an hepatic tocopherolbinding protein in Atlantic salmon (Salmo salar L.) (1998)
    Springer
    Fish physiology and biochemistry 18 (1998), S. 71-83 
    Details
    ISSN: 1573-5168
    Keywords: vitamin E ; tocopherol ; Atlantic salmon ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The purpose of this work was to study the turnover of a, γ andδtocopherol (TOH) in Atlantic salmon (Salmo salar, L.). Fish induplicate tanks were fed a diet containing 150 mg kg-1α-TOH and 100 mg kg-1 each of γ and δTOHadded as tocopheryl acetates. After fillet TOH concentrations had adjustedto the dietary supplementation levels, samples were taken from fish that hadbeen deprived of feed for 100 h, and from fish that had been fed regularlyuntil sampling. The retained levels of tocopherols in plasma correspondedgrossly with their biological activities, as found in experiments withmammals (α:γ:δ≈100: 20:3). The plasma concentrationsof α-, γ and δTOH amounted to 65, 44 and 15%,respectively, in unfed compared to fed fish. Very low density lipoprotein(VLDL), appeared to contain a greater fraction of plasma α-TOH than ofplasma δTOH. The mitochondrial fraction of liver, but not that of darkmuscle, was highly enriched in α-TOH, and less in γ andδTOH. The concentration ratios in liver and bile indicate thatδ, and to some extent, γTOH are excreted in the bile at a higherrate than α-TOH. The data fit the hypothesis that Atlantic salmonliver contains a tocopherol binding protein with higher affinity forα-TOH than for the other tocopherol homologues. This appears toprevent excretion of α-TOH in the bile, and stimulate incorporation ofα-TOH in VLDL for subsequent secretion into the blood stream. As aconsequence, α-TOH is retained in the body to a greater extent thanγ and α-TOH.
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    URL: http://dx.doi.org/10.1023/A:1007798102002
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    Comparative study of iodothyronine outer ring and inner ring deiodinase activities in five teleostean fishes (1998)
    Springer
    Fish physiology and biochemistry 18 (1998), S. 253-266 
    Details
    ISSN: 1573-5168
    Keywords: thyroid hormone ; iodothyronines ; deiodination ; fish ; tilapia ; trout ; catfish ; turbot
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The presence of outer ring deiodinating (ORD) and inner ring deiodinating (IRD) activities was investigated in different tissues of Oreochromis niloticus (Nile tilapia), Clarias gariepinus (African catfish), Oncorhynchus mykiss (rainbow trout) and halmus maximus (turbot). High-Km rT3 ORD is present in the kidney of most of the fishes studied, except in catfish. In turbot, besides the kidney, rT3 ORD is also present in liver, heart and ovary. Low-Km T4 ORD is found in the liver and low-Km T3 IR the brain of all the fishes studied. In addition, low levels of low-Km T3 IRD were demonstrated in gill and skin of Nile tilapia, liver of rainbow trout and gill and kidney of turbot. For the different teleosts, the biochemical properties of the different rT3-deiodinating enzymes mentioned, T4 ORD in liver and T3 IRD in brain and tilapia gill were compared to those of the deiodinases formerly characterized in Oreochromis aureus (blue tilapia). In general, the different deiodinases demonstrate analogous sensitivities to iodothyronines and inhibitors, although minor differences occur. The various deiodinating enzymes all depend on addition of dithiothreitol and demonstrate maximal activity pH between 6.5 and 7. The optimal incubation temperature of rT3 ORD and T4 ORD in tilapia and catfish is 37 °C, in trout and turbot it varies, depending on the tissue, between 25 ° and 37 °C. For the different T3 IRD activities the optimal temperature is 37 °C in warmwater as well as in coldwater species. The apparent Km values for rT3 ORD lay in the μM range, for T4 ORD and T3 IRD they lay in the nM range. Vmax values are usually higher in tilapia as compared to the other teleosts studied. Based on the similarities in susceptibility to inhibition by different iodothyronines and inhibitors and the agreement of the apparent Km values, we conclude that the deiodinating enzymes in teleosts are more similar to mammalian deiodinases than is generally accepted.
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    URL: http://dx.doi.org/10.1023/A:1007722812697
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    The wheat germ agglutinin binding sites and development of the mitochondria-rich cells in gills of tilapia (Oreochromis mossambicus) (1998)
    Springer
    Fish physiology and biochemistry 19 (1998), S. 95-102 
    Details
    ISSN: 1573-5168
    Keywords: mitochondria-rich cell ; wheat germ agglutinin ; bromo-deoxyuridine ; calcium ; gill ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By labelling with gold-colloid-conjugated wheat germ agglutinin (WGA), the WGA-binding sites were identified in the apical region of certain mitochondria-rich (MR) cells in gills of freshwater-adapted tilapia (Oreochromis mossambicus). Bromo-deoxyuridine (BrdU) injection was used to discern the differentiation of the WGA binding sites during development of MR cells. Double labeling of gill sections of fish 2, 4, 6, and 8 days after a single BrdU injection showed that the BrdU labeled MR cells 2 and 4 days after injection were mostly WGA negative, whereas 6 and 8 days after injection, WGA and BrdU-labeled MR cell increased gradually in number. Furthermore, the ratio of the WGA-positive to total MR-cells was higher in gills of tilapia adapted to low calcium ([Ca] = 0.015 mm) freshwater than in hard freshwater ([Ca] = 1.898 mm). The results indicate that WGA binding site may be a marker expressed late during differentiation of MR cells, and physiologically functional in assisting uptake of calcium when environmental calcium is low. According to their WGA binding and also characteristics their likely function in calcium absorption, the WGA positive MR cells shown in this study are considered to be similar to the β cells described by Pisam et al. (1995).
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    What determines the size of teleost erythrocytes? Correlations with oxygen transport and nuclear volume (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 31-35 
    Details
    ISSN: 1573-5168
    Keywords: aerobic scope ; blood ; erythrocyte volume ; fish ; haemoglobin ; metabolism ; nuclear volume ; oxygen transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An inverse relationship exists between erythrocyte size and the aerobic swimming ability of teleosts. A functional basis for this relationship is found in larger surface area to volume ratios and shorter diffusion distances allowing more rapid oxygen transfer as erythrocyte volume decreases. However, this apparently simple functional relationship is confounded by a more general direct relationship between cell size and nuclear volume. Nuclear DNA content, which is directly proportional to nuclear volume, is known to vary at least 11 fold among teleost species. Therefore a question arises as to the relative contributions of nuclear volume and the demands of the blood oxygen delivery system in determining erythrocyte volume. These relationships were investigated by regressing erythrocyte volume against nuclear volume and whole blood haemoglobin concentration (as an index of aerobic scope) for 52 species of teleost fish from 25 families. This analysis shows that erythrocyte volume is more highly correlated with oxygen delivery than with nuclear volume. However, much of the variation in erythrocyte volume is unexplained.
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    URL: http://dx.doi.org/10.1023/A:1007785202280
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    Effects of experimental hypo- and hyperthyroidism on iodothyronine deiodinases in Nile tilapia, Oreochromis niloticus (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 201-207 
    Details
    ISSN: 1573-5168
    Keywords: thyroid hormone ; deiodination ; fish ; tilapia ; hyperthyroidism ; hypothyroidism ; methimazole ; porcine follicle stimulating hormone ; T3 ; T4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the present study, we examined the effects of experimentally-induced increases or decreases in plasma concentrations of thyroid hormones on iodothyronine deiodinases in tilapia, Oreochromis niloticus. To obtain hyperthyroid tilapia, fish were injected with porcine follicle stimulating hormone (pFSH) 36 hours before sampling or fed on demand for 11 days with tilapia pellets containing 12 ppm T3. Tilapias were made hypothyroid by providing them food containing 0.2% methimazole for 11 days. Plasma T4 and T3 and the in vitro deiodinase activity in liver, kidney, brain and gill were measured at the end of the treatment period. Injection with pFSH caused an increase in plasma T4 but had no influence on plasma T3 levels. A small increase in plasma T3 was observed in T3-fed fish. Plasma levels of both T4 and T3 were decreased by methimazole treatment. We observed no changes in kidney type I deiodinase (D1), whereas liver type II deiodinase (D2) was increased during hypothyroidism and decreased during hyperthyroidism. Hypothyroidism resulted in a significant decrease in brain, gill and liver type III deiodinase (D3). An pFSH-induced increase in T4 stimulated brain and gill D3 but not liver D3, whereas the opposite was true in T3-fed fish. We conclude that the regulation of D1 and D3 in tilapia is probably different compared to mammals.
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    Biochemical characterization of growth hormone receptor in rainbow trout (Oncorhynchus mykiss) before and after purification (1999)
    Springer
    Fish physiology and biochemistry 21 (1999), S. 111-120 
    Details
    ISSN: 1573-5168
    Keywords: fish ; GH ; GH-R ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this work was to verify if, compared to mammals, the lower molecular weight of GH-R previously reported in salmonid is real or due to the experimental process. For this purpose, we compared the apparent molecular weight of GH-R, obtained by SDS-PAGE after cross-linking with 50 I-rtGH, obtained from rainbow trout crude liver membrane preparation, incubated in different buffers with those obtained after purification with affinity chromatography. Using crude liver membrane preparation, two specific bands of 50 I-rtGH-protein complex were observed: the major one corresponds to a MW of 70 kDa and the minor one to 45 kDa. However, the pattern of electrophoresis varied according to the different incubation buffers tested. Digestion of the cross-linked complex with β-galactosidase and phospholipase did not significantly modify the position of bands, whilst N-glycosidase F induced a large smear including 4 more pronounced bands (50, 65, 97 and 〉 130 kDa), the heavier band corresponding to the most intensive signal. GH receptors were purified using solubilisation and affinity chromatography. The yield of the liver GH-R from crude liver membrane preparation by the solubilization technique was optimized (48%) using Triton 1% for 1 h (12 °C ). Specific binding sites in the solubilized membrane proteins were saturable when incubated with increasing 50 I-rtGH concentrations, and revealed a high affinity constant (Ka=0.7×109 M−1). After affinity chromatography, specific binding activity was increased 64,000 fold. However, the purity of the preparation was partial and the purification yield was very low (about 0.3%). This enriched fraction, analysed by SDS-PAGE after cross-linking, showed a very intense band (about 63 kDa) which disappeared with an excess of cold rtGH. These results suggest that the lower molecular weight observed in salmonid (41 kDa), compared to mamals, is not due to the experimental process. The significance of GH-R size difference between salmonids and mammals is discussed.
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    URL: http://dx.doi.org/10.1023/A:1007733723430
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    Fish hepatocyte glycogen phosphorylase – a sensitive indicator for hormonal modulation (1999)
    Springer
    Fish physiology and biochemistry 21 (1999), S. 15-24 
    Details
    ISSN: 1573-5168
    Keywords: caffeine ; catecholamines ; fish ; glucose production ; liver ; method/assay ; phosphorylation ; prostaglandin E2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The absence of a reproducible method for the assay of glycogen phosphorylase (GPase) in isolated fish hepatocytes has made the interpretation of hormone-induced glycogenolysis data difficult. This study presents such an assay and demonstrates its sensitivity to hormonal activation. The enzyme is assayed in the reverse direction using glucose 1-phosphate (G1-P) and glycogen as substrates and uses standard methods for the quantification of the liberated inorganic phosphate. The assay is highly reproducible, sensitive, and provides an excellent means to follow small and rapid changes in enzyme phosphorylation status following the addition of hormones. We show for hepatocytes isolated from rockfish (Sebastes caurinus) and brown bullhead (Ameiurus (Ictalurus) nebulosus) that small concentrations of three model hormones, namely epinephrine (catfish), norepinephrine, and prostaglandin E2 (rockfish), lead to the rapid, concentration and time-dependent conversion of existing GPase into the active GPase a form. Some of the enzyme seems to be impervious to hormonal activation, as the highest %GPase a never reaches 100%. We provide evidence that changes in enzyme phosphorylation status provide a better short-term insight into hormone-dependent activation than estimates of glucose or some other end products, that usually must accumulate for long periods before detection is possible. Our data also show that GPase in freshly isolated hepatocytes is already in an activated state and cells should be given a period of ‘rest’ for several hours before hormonal studies involving glycogen breakdown or the cAMP cascade are initiated.
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    Diel changes in plasma arginine vasotocin, isotocin, and melatonin in rainbow trout (Oncorhynchus mykiss) (1999)
    Springer
    Fish physiology and biochemistry 21 (1999), S. 141-146 
    Details
    ISSN: 1573-5168
    Keywords: fish ; hormones ; neurohypophysis ; pineal organ ; rhythm ; teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diel changes in plasma AVT, IT and Mel in rainbow trout (Oncorhynchus mykiss) were studied to assess potential relationships. Blood was sampled at 05:00, 11:00, 16:00, 22:30 and 05:00 in freshwater-adapted fish and at 22:30 in brackish water-adapted fish maintained under natural photoperiod. A few of the FW-acclimated fish were assigned to one of two experimental groups and adapted to DD or LL lighting regimes. Blood samples were taken at 11:00 and 22:30. Hormones were extracted from plasma by solid phase extraction and determined by high-performance liquid chromatography. Marked diel variations in AVT and Mel were detected in fish maintained under natural photoperiod. Plasma AVT (fmol ml−1) increased during the light to reach the maximal level at the end of that phase (261.7±23.1). Thereafter, AVT concentration decreased and became minimal at 05:00 (68.9±11.5) 3 h before the sunrise. Plasma Mel (pmol ml−1) increased between 16:00 and 22:30 when a peak value was reached (1204.0±55.5). Thereafter, Mel levels decreased and were minimal after the onset of the light phase (242.8±37.0). IT levels displayed no significant diel changes. Linear regression analysis indicated the negative correlation between plasma Mel and AVT for five collecting times of the daily 24 h cycle in freshwater fish and at 22:30 in brackish water fish. A similar correlation occurred at 11:00 in the DD group and at 22:30 in the LL group. To elucidate the character of the Mel-AVT relationships further studies are required.
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    Metabolic enzyme activities in larvae of the African catfish, Clarias gariepinus: changes in relation to age and nutrition (1995)
    Springer
    Fish physiology and biochemistry 14 (1995), S. 385-398 
    Details
    ISSN: 1573-5168
    Keywords: fish ; Clarias gariepinus ; ontogenesis ; nutrition ; metabolism ; NADPH generation ; aerobic metabolism ; amino acid catabolism ; glycolysis ; gluconeogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of ontogeny and nutrition on metabolic enzyme activities in larvae of the African catfish, Clarias gariepinus, was studied. After start of exogenous feeding, the larvae were reared for 10 days under three different nutritional conditions: Artemia nauplii, a dry starter diet, and starvation. The live feed gave the best growth (96 mg within 10 days) whereas the dry diet resulted in low growth (33 mg). This growth difference was reflected in larval RNA and DNA concentrations, but not in the levels of soluble protein. Enzymes representing the following aspects of metabolism have been analysed: NADPH generation (G6PDH, ME), glycolysis (PFK, PK), gluconeogenesis (FDPase), amino acid catabolism (GOT, GPT) and oxidative catabolism (CS). All enzymes were present from the start of exogenous feeding onwards, but their maximum specific activities displayed different developmental patterns. In catfish larvae fed on Artemia, G6PDH and ME activities steadily increased with age and weight of the larvae. CS levels remained, after an immediate enhancement upon onset of exogenous feeding, on a rather stable plateau. The amino acid-degrading enzymes GOT and GPT showed maximum levels at days 3–5 of feeding or at a body weight of 10–20 mg, but decreased thereafter. Activities of PFK, PK and FDPase showed low initial levels, and increased significantly with age and size. Based on the ontogenetic patterns of metabolic enzymes, in C. gariepinus larvae an early and a late developmental phase can be distinguished. During the early phase, the glycolytic and gluconeogenetic capacities are low, whereas they are enforced during the later phase. The oxidative capacity is high both during the early and the late phase. The metabolic changes in catfish development coincide with other major ontogenetic events, e.g., alterations of muscle organization, gill morphology, respiration and stomach structure and function. Rearing catfish larvae on a dry diet instead of Artemia partly altered the developmental pattern described: The ontogenetic elevation of CS, PFK and FDPase was delayed and the early peak in GOT and GPT activities was not realized. Particularly during the early developmental phase, the enzyme behaviour of the larvae fed on dry food was similar to that of starved larvae.
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    Modelling spatial dynamics of fish (1998)
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    Reviews in fish biology and fisheries 8 (1998), S. 57-91 
    Details
    ISSN: 1573-5184
    Keywords: adaptation ; artificial neural networks ; fish ; fitness ; game theory ; genetic algorithms ; hearing ; ideal free distribution ; learning ; life history theory ; memory ; migration ; olfaction ; optimal foraging theory ; optimization ; sensory organs ; spatial modelling ; stochastic dynamic programming ; vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Our ability to model spatial distributions of fish populations is reviewed by describing the available modelling tools. Ultimate models of the individual's motivation for behavioural decisions are derived from evolutionary ecology. Mechanistic models for how fish sense and may respond to their surroundings are presented for vision, olfaction, hearing, the lateral line and other sensory organs. Models for learning and memory are presented, based both upon evolutionary optimization premises and upon neurological information processing and decision making. Functional tools for modelling behaviour and life histories can be categorized as belonging to an optimization or an adaptation approach. Among optimization tools, optimal foraging theory, life history theory, ideal free distribution, game theory and stochastic dynamic programming are presented. Among adaptation tools, genetic algorithms and the combination with artificial neural networks are described. The review advocates the combination of evolutionary and neurological approaches to modelling spatial dynamics of fish.
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    Long-term changes in crustacean zooplankton and water quality in a shallow, eutrophic Chinese lake densely stocked with fish (1998)
    Springer
    Hydrobiologia 391 (1998), S. 193-201 
    Details
    ISSN: 1573-5117
    Keywords: crustacean zooplankton ; long-term changes ; water quality ; fish ; Lake Donghu ; China
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From surveys made in 1962–1963, 1973–1974, 1979–1996 at two Stations in Lake Donghu, a shallow eutrophic water body near Wuhan, P. R. China, the authors, derive long-term changes in species composition, standing crop and body-size of planktonic crustaceans. The species number decreased from the 1960s to the 1990s. The cladocerans dropped from 46 (1960s) to 26 (1980s) to 13 (1990s); the copepods decreased from 14 (1960s) to 10 (1980s) to 7 (1990s). From the mid-1980s on, the dominant crustaceans also changed: Daphnia hyalina and D. carinata ssp. were replaced by Moina micrura and Diaphanosoma brachyurum at Stations 1 and 2, respectively; Cyclops vicinus replaced Mesocyclops leuckarti. Densities and biomass of Cladocera decreased markedly after 1987. Annual average densities and biomass of cladocerans were statistically differences between 1962–1986 and 1987–1996 (P 〉 0.01). Annual average densities of Daphnia (Station 1 + Station 2) were negatively correlated with fish yield . Since the 1980s, annual average body length of Cladocera and Calanoida decreased, while annual average body length of Cyclopoida increased. In the same years, average body length of copepods was lower during May–October than during January–April and November–December. A 12-yr data analysis showed annual average concentration of chlorophyll-a (Chl-a) to be negatively correlated with annual average density of Daphnia, whilst lake transparency was positively correlated with annual average densities of Daphnia. The results imply that, since Daphnia feeds efficiently on phytoplankton, it could decrease concentration of Chl-a, and enhance water transparency.
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    Size-dependent over-winter mortality of young-of-the-year roach, Rutilus rutilus (1997)
    Springer
    Environmental biology of fishes 50 (1997), S. 451-456 
    Details
    ISSN: 1573-5133
    Keywords: energy reserves ; fasting ; starving ; Lake Isojärvi ; Lake Päijänne ; fish ; cyprinid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Over-winter survival of starved and fed young-of-the-year roach from two lakes in central Finland was examined in the laboratory between November 1992 and May 1993. The mortality rate of starving YOY roach (total length 38 ± 2 mm) from small (ca. 0.5 km2), eutrophic Lake Isojärvi was 50%, whilst roach (total length 32 ± 3 mm) from large Lake Päijänne (1106 km2) suffered 42% mortality. Mortality was size-dependent among roach from Lake Isojärvi, smaller individuals being more vulnerable. There was not strict size limit for survival as proposed previously. However, it seems that within populations approximately the same proportion of smallest roach died independent of the absolute lengths of the fish. Mortality of fed roach from both lakes was always 〈 5%. This good survival indicates indirectly the importance of energy reserves in wintering. Lipid and protein content of fasting roach from lake Isojärvi decreased during the winter. In the group of fasting roach from Lake Päijänne the amount of lipids stored increased between November and March and decreased thereafter. No change in protein content of fasting fish from Lake Päijänne was observed.
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    Simulating smallmouth bass reproductive success in reservoirs (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 161-174 
    Details
    ISSN: 1573-5133
    Keywords: Micropterus dolomieu ; reproduction ; predictive model ; Brownlee Reservoir ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An individual-based model of nesting smallmouth bass, Micropterus dolomieu, is used to predict the effects of water level fluctuations on reproductive success. The model simulates daily nest site selection, spawning, nest guarding, and development and survival of eggs, embryos, and larvae until dispersal. The model was configured for Brownlee Reservoir, Idaho-Oregon. Each reservoir bank is represented as a rectangular grid of cells, with each cell characterized by an assigned slope, substrate, and elevation, and by a water depth that varied daily. Nest site (cell) selection is determined from a habitat suitability index (HSI) based on substrate, slope, and depth. Development of young is temperature-dependent. Mortality of young occurs via attrition, abandonment by the guarding male, and probabilistic whole-nest catastrophe. Simulations were performed that used observed data for 1991 to 1996. Model predicted nest habitat selection and egg-to-dispersal survival rates were similar to observed values. Additional model simulations showed that: (1) nest habitat selection was best predicted when depth, slope, and substrate were considered together rather than singly, (2) egg-to-dispersal survival was related to the magnitude of water level fluctuations during the peak spawning period, (3) relating mortality to HSI values resulted in lower survival, while relating growth to HSI values resulted in higher survival, and (4) spawning habitat is not limiting in Brownlee Reservoir. Suggestions for future monitoring of reservoir-based smallmouth bass populations are discussed.
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    Gastric evacuation rates and maximum daily rations of rainbow trout fed chironomid larvae at 7.8, 10.0 and 12.8°C (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 321-330 
    Details
    ISSN: 1573-5133
    Keywords: food consumption ; Salmo gairdneri ; Oncorhynchus mykiss ; fish ; stream population
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gastric evacuation rate (GER) and maximum daily ration (CMAX) data for rainbow trout, Oncorhynchus mykiss, are scant, particularly those that apply to field populations of this species. We determined GERs and CMAXs of rainbow trout (approx. 160-300 mm TL, 40-300 g live weight), fed chironomid larvae at 7.8, 10.0 and 12.8°C. Primary GER and CMAX results are provided so they can be readily compared and combined with data from related studies. Disclosure of primary data should facilitate development of predictive equations for GER and CMAX that are applicable to the broad array of conditions under which rainbow trout exist. Our GERs at 10°C were intermediate to but different from most reported in other such studies of rainbow trout at this temperature where different food types were used. Our CMAX values for rainbow trout were substantially higher than those reported in a previous study, and we argue that our values are probably more appropriate for stream-dwelling populations. We also provide evidence that Elliott's (1972, 1975) equations for predicting GER and CMAX in brown trout, Salmo trutta, should not be applied to rainbow trout as has been done in some studies.
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    Reproductive success in female Neolamprologus mondabu (Cichlidae): influence of substrate types (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 261-269 
    Details
    ISSN: 1573-5133
    Keywords: substrate brooder ; body size ; home range size ; habitat preference ; Lake Tanganyika ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Individual variation in body size, home range size, and reproductive success among Neolamprologus mondabu (Cichlidae) females were investigated with reference to substrate types in the littoral zone of northern Lake Tanganyika. Larger females occupied sandy substrates and smaller ones stony substrates. Female reproductive success, estimated as the number of offspring successfully released per month, was higher on sandy substrates than on stony substrates. This may be attributable to higher spawning intensity and better protection of broods against predators in open, sandy habitats.
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    Dyadic relationships in nesting males of the three-spined stickleback, Gasterosteus aculeatus (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 243-250 
    Details
    ISSN: 1573-5133
    Keywords: dyad ; aggressive interaction ; social relationships ; nesting males ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Multidimensional scaling analysis of nest site location, nesting interval, and aggressive and mating interactions revealed that male three-spined sticklebacks, Gasterosteus aculeatus, formed nesting clusters comprising five patterns of dyadic relationships. These patterns were defined by intervening variables such as size difference between the two males, nest site locations, synchronization of nesting cycles (egg presence in the nest), distance between two nests, and nest raiding behaviours. Several patterns of dyadic relationships were integrated among nesting males and their constellations indicated an expression of the social structure. Through an understanding the social structure, I described effects of social context or situations on individual reproductive success.
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    Daily spawning and development of sensitivity to gonadotropin and maturation-inducing steroid in the oocytes of the bambooleaf wrasse, Pseudolabrus japonicus (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 281-290 
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    ISSN: 1573-5133
    Keywords: maturational competence ; protogyny ; teleost ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cycle of oocyte development of the bambooleaf wrasse, Pseudolabrus japonicus, was studied to elucidate the endocrinological mechanism of oocyte maturation in a marine teleost. A single female reared with two males spawned every day for 17 days in captivity, indicating that this species is a daily spawner. Ovarian histology revealed that germinal vesicle migration of the largest oocytes progressed from 12:00 to 3:00 h, and germinal vesicle breakdown (GVBD) was completed at 6:00 h. Ovulation and spawning occurred between 6:00 and 9:00 h. The effectiveness of human chorionic gonadotropin (HCG) and 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P), which is one of the most potent steroidal inducers of GVBD in bambooleaf wrasse oocytes, in inducing final oocyte maturation was examined at eight different times of the day. The responsiveness of the oocyte to HCG and steroid differed at different times of the day. The GVBD could be induced by HCG but not 17,20β-P at 9:00 h. Between 12:00 and 18:00 h, not only HCG but also 17,20β-P induced GVBD. Both GVBD and ovulation spontaneously occurred between 0:00 and 6:00 h without any hormonal treatment. These results clearly showed that the oocyte of the bambooleaf wrasse possessed a diurnal maturation cycle. Responsiveness of oocytes to HCG appeared earlier than responsiveness to 17,20β-P. This suggests that sensitivity to 17,20 β-P is induced by gonadotropic hormone (GTH).
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    URL: http://dx.doi.org/10.1023/A:1007424103444
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    Osteology of Zacco pachycephalus, sensu Jordan & Evermann (1903), with special reference to its systematic position (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 163-171 
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    ISSN: 1573-5133
    Keywords: Formosan cyprinid ; skeletal system ; Opsariichthys ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The skeletal system of Zacco pachycephalus, sensu Jordan & Evermann (1903), is described and compared with that of other related barilines to clarify its systematic position. Osteological characters fall generally into two categories in terms of apomorphic features. The first category is exemplified by autapomorphies such as lower jaw bone shape and the number of branchiostegal rays and hypurals. The latter characters are highly unusual among Cyprinidae. The second category consists of synapomorphies linking Z. pachycephalus and Opsariichthys uncirostris. Specialization of jaw bones for a piscivorous habit is also notable. The quadrate-pterygoid fenestra of Z. pachycephalus and O. uncirostris is considered derived. We conclude that Zacco pachycephalus should be transferred from Zacco to Opsariichthys based on the present osteological analysis.
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    Home range of the Japanese fluvial sculpin, Cottus pollux, in relation to nocturnal activity patterns (1998)
    Springer
    Environmental biology of fishes 53 (1998), S. 295-301 
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    ISSN: 1573-5133
    Keywords: appearance ; residential tendency ; substratum use ; nocturnal activity ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Patterns of space use related to the activity of individual Japanese fluvial sculpins, Cottus pollux, were examined during the non-breeding season, in the upper reaches of the Inabe River, central Japan. Sculpins appeared more frequently at night than in daytime. Among 31 recaptured sculpins, 30 (96.8%) showed nocturnal activity patterns, there being no fish which exhibited an entirely diurnal activity pattern. Of 21 sculpins captured both in daytime and at night, the most common pattern of space use (n = 14, 66.7%) was that in which the nocturnal home range entirely encompassed the diurnal range. Overall, nocturnal home ranges were significantly larger than diurnal ranges. Active sculpins were rarely found on sand-associated substrata in daytime, but were seen more frequently on such substrata at night.
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    URL: http://dx.doi.org/10.1023/A:1007410519726
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    Effects of substrata, resident conspecifics and damselfish on the settlement and recruitment of the stoplight parrotfish, Sparisoma viride (1998)
    Springer
    Environmental biology of fishes 53 (1998), S. 393-404 
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    ISSN: 1573-5133
    Keywords: pre-settlement ; post-settlement ; Caribbean ; microhabitat ; coral reef ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recruitment plays an important role in the population dynamics of marine organisms and is often quantified as a surrogate for settlement. When quantified, recruitment includes settlement plus a period of time in the benthic habitat. Therefore, it is essential to determine whether post-settlement processes alter patterns established at settlement. I conducted a series of experiments on 2.0 m2 patch reefs to examine the importance of pre- and post-settlement processes to the distribution and abundance of recruits of the stoplight parrotfish, Sparisoma viride, on the Tague Bay reef, St. Croix, USVI. Recruitment was higher to the coral Porites porites than to another common coral Montastrea annularis, but there was no evidence of microhabitat choice at settlement. This result, in conjunction with the examination of the size classes of recruits present on P. porites and M. annularis patch reefs in a separate experiment suggested that differences in recruitment were established after settlement. Stoplights settled in higher numbers to patch reefs that contained conspecific residents, and persistence was higher at higher recruit density. Although resident damselfish directed significant amounts of agonistic behavior towards newly stoplight recruits, damselfish presence had no effect on settlement. However, damselfish presence did reduce stoplight recruitment. These results demonstrate that both pre- and post-settlement processes influence the recruitment of stoplight parrotfish. More importantly, these results indicate that benthic processes can alter recruitment patterns from initial settlement patterns, and indicate that workers should be careful in using recruitment as a proxy for settlement.
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    Intraspecific Variations in Size- and Age-at-maturity for Red Bandfish, Cepola macrophthalma (1999)
    Springer
    Environmental biology of fishes 54 (1999), S. 151-160 
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    ISSN: 1573-5133
    Keywords: Aegean Sea ; length-at-maturity ; intraspecific variations ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intraspecific variations in size- and age-at-maturity were studied in red bandfish, Cepola macrophthalma, in two adjacent gulfs of the western Aegean Sea, in the southern of which the population of red bandfish is stunted. Samples were collected with a commercial trawler over a grid of 34 stations at depths ranging from 22 to 222 m. The hypothesis tested was that length and age at 50% maturity, Lm50 and tm50 respectively, for males and females do not differ in the two regions. The results showed that the Lm50 of both males and females in the northern area was by 3.5 cm larger than that in the southern area and the 95% confidence intervals of Lm50 in the two areas did not overlap. Although the tm50 of males was larger in the northern area, the 95% confidence intervals of tm50 overlapped in the two areas whereas for females, the tm50 was larger by 0.4 years in the northern area and the 95% confidence intervals of tm50 in the two areas did not overlap. Stunting of the red bandfish growth in the southern area is the result of the combination of an extremely low food availability with higher temperatures prevailing in that area. Implications of these fine spatial scale intraspecific differences for the fisheries management of the highly oligotrophic eastern Mediterranean Sea are also discussed.
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    URL: http://dx.doi.org/10.1023/A:1007594719450
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    Fall and Early Winter Movements of Cutthroat Trout, Oncorhynchus clarki, in Relation to Water Temperature and Ice Conditions in Dutch Creek, Alberta (1999)
    Springer
    Environmental biology of fishes 55 (1999), S. 359-368 
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    ISSN: 1573-5133
    Keywords: fish ; salmonid ; aggregation ; anchor ice ; groundwater ; behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fall and winter movement and behaviour of 28 cutthroat trout Oncorhynchus clarki was determined using radiotelemetry to evaluate the effects of water temperature and ice conditions. As water temperatures decreased, cutthroat trout moved from more solitary positions to aggregations. With few exceptions, radiotagged fish aggregated with other fish in groups varying from 5 to approximately 70 fish. The percentage of fish aggregating and the mean size of aggregation was negatively correlated with water temperature. The mean distance moved by radiotagged cutthroat trout from 1 September to 12 January was 1.0 km. After forming aggregations, fish tended to stay within a 120 m length of stream until the end of tracking in mid-January. Fish that were less sedentary after their initial overwintering movement usually moved when their habitat was occluded by anchor ice. These fish moved thirty times farther and six times more often than fish in stable overwintering areas. In Dutch Creek multiple freezing events caused several ice related habitat exclusions and movements associated with large decreases in air temperature. Several bull trout and mountain whitefish were observed in groups with cutthroat trout.
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    Variation in Gillraker Number During Growth of the Sea Bass, Dicentrarchus labrax (Perciformes: Moronidae), Reared at Different Salinities (1999)
    Springer
    Environmental biology of fishes 55 (1999), S. 391-398 
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    ISSN: 1573-5133
    Keywords: ecophenotypism ; branchial sieve ; geographic variation ; fish ; meristics ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A marked salinity-related decrease in gillraker number in sea bass samples during growth was documented. All specimens share the same genetic stock and rearing conditions were constant during early ontogeny. Variation in gillraker number could be related to the ecophenotypism of this character but selection can not be excluded. Results obtained from reared specimens were compared with those reported in the literature and with data collected from wild stocks. Attention is focused on the pitfalls that the use of this character may have on the taxonomy of fish species.
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    URL: http://dx.doi.org/10.1023/A:1007548102060
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    Aspects of the Feeding and Reproductive Biology of the Lake Tanganyikan Cichlid, Lamprologus ornatipinnis (Pisces, Cichlidae) (1999)
    Springer
    Environmental biology of fishes 55 (1999), S. 431-441 
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    ISSN: 1573-5133
    Keywords: diet ; gonadosomatic index ; seasonality ; dentition ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This project investigated the reproductive and feeding biology of Lamprologus ornatipinnis. Specimens were collected monthly from North Bay, Mbita Island, Zambia for a year. Dentition was examined under a scanning electron microscope, stomach contents were analysed using the Index of Relative Importance (IRI) and mean Gonado-somatic Indices (GSI) were calculated for each month to reveal spawning peaks. Both males and females possess an outer row of six (premaxilla) and eight (dentary) enlarged canines. The remaining inner rows consist of small, recurved canine-like teeth. The lower pharyngeal bone possesses enlarged centrally placed molars with an increasing number of smaller bevelled teeth laterally. This dentition is very similar to a typical benthic arthropod and mollusc eater. Stomach content analysis revealed that L. ornatipinnis feeds predominantly on Chironomidae, Copepoda and Ostracoda. The importance of these prey items in the diet differed significantly between the months sampled. Percentage volume of Copepoda and Cyclopoida was greater in female stomachs than males and the % number of Chironomidae greater in males than females. Gonadosomatic Index (GSI) values indicated males and females breed throughout the year. Females, however have a significant peak (p〈0.05) in breeding activity from July to October that coincides with the increased abundance of plankton at this time.
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    URL: http://dx.doi.org/10.1023/A:1007540121262
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    Arrival of an Australian anguillid eel in New Zealand: an example of transoceanic dispersal (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 1-6 
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    ISSN: 1573-5133
    Keywords: biogeography ; Anguilla ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Anguilla reinhardtii, hitherto known from eastern Australia, New Caledonia, Norfolk Island, and Lord Howe Island, has recently been discovered in rivers of northern New Zealand. Identification, based on morphological and genetic characteristics, is unequivocal; eight consecutive year classes have been found. The only reasonable explanation of this occurrence is transoceanic dispersal to New Zealand, probably from subtropical oceanic spawning grounds north of New Zealand. This corroborates past hypotheses that the strongly diadromous freshwater fish fauna of New Zealand is derived by transoceanic dispersal of known marine life intervals.
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    URL: http://dx.doi.org/10.1023/A:1007326405148
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    Sound production during feeding in Hippocampus seahorses (Syngnathidae) (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 221-229 
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    ISSN: 1573-5133
    Keywords: bioacoustics ; feeding behavior ; functional morphology ; fish ; cavitation ; stridulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract While there have been many anecdotal reports of sounds produced by Hippocampus seahorses, little is known about the mechanisms of sound production. We investigated clicking sounds produced during feeding strikes in H. zosterae and H. erectus. Descriptions of head morphology support the idea that feeding clicks may represent stridulatory sounds produced by a bony articulation between the supraoccipital ridge of the neurocranium and the grooved anterior margin of the coronet. Analysis of high-speed video and synchronous sound recordings of H. erectus indicate that the feeding click begins within 1-2 msec of the onset of the rapid feeding strike (4 msec mean duration). Surgical manipulations of the supraoccipital-coronet articulation resulted in a decreased proportion of feeding strikes that produced clicks. This study provides several lines of evidence in support of the hypothesis that feeding clicks in Hippocampus seahorses are stridulatory in origin and are produced by the supraoccipital-coronet articulation. Our results are not consistent with previous suggestions that sounds may be produced by cavitation due to rapid pressure changes within the buccal cavity during the feeding strike.
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    Comparative ecology and historical biogeography of the genus Brachyrhaphis (1998)
    Springer
    Environmental biology of fishes 51 (1998), S. 117-127 
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    ISSN: 1573-5133
    Keywords: poeciliid ; area cladogram ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phylogenetic systematics was used to reveal micro-evolutionary processes and macro-evolutionary patterns that have resulted in the current distribution of species of the live-bearing fish genus Brachyrhaphis. A previously constructed molecular phylogeny for the genus determined that two distinct clades, deep-bodied and slender-bodied, exist within the genus. Micro-habitat variables were measured for all extant members of the genus. Water flow differed significantly between the clades and was converted to a discrete variable and, along with elevation and micro-habitat type, mapped onto the phylogeny for the genus. The evolution of micro-habitat choice was hypothesized using these results. A detailed distribution map was constructed to unveil biogeographic patterns and was also interpreted in light of the molecular phylogeny. The phylogeny was then used to construct an area cladogram. This cladogram was compared to the one derived from paleogeography. The molecular-based area cladogram adds to the growing database required to resolve the biogeography of the Caribbean.
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    URL: http://dx.doi.org/10.1023/A:1007415928796
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    Response to Video and Computer-animated Images by the Tiger Barb, Puntius tetrazona (1999)
    Springer
    Environmental biology of fishes 56 (1999), S. 317-324 
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    ISSN: 1573-5133
    Keywords: video playback ; television ; schooling behavior ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Video playback has become an important tool for testing certain questions about animal visual perception. While a few studies have compared the response of test subjects to live and video stimuli, it is generally assumed a priori that the animals will respond to the video image as if it were ‘real’. Since video devices are tuned to the spectral sensitivities and flicker fusion frequencies of the human eye and brain, it is important to conduct preliminary tests to compare the response of test subjects between live and video images. Here we compare schooling behavior of tiger barbs, Puntius tetrazona, when presented with a school of live fish, an analog video school of fish and a video of a computer-animated school of fish. Test subjects did not show a significantly different schooling behavior response to any of these stimuli. Additionally, when given the choice of schooling with a conspecific versus a heterospecific, tiger barbs schooled significantly more often with the conspecifics for all three stimulus formats. This study provides evidence that tiger barbs do not choose to discriminate between live and video models of fish and that this technique can be used to test future questions concerning visual perception for this species.
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    A Sexual Preference in the Amazon Molly, Poecilia formosa (1999)
    Springer
    Environmental biology of fishes 56 (1999), S. 325-331 
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    ISSN: 1573-5133
    Keywords: video-playback ; Poeciliidae ; mate choice ; sexual selection ; gynogen ; fish ; ontogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Amazon molly, Poecilia formosa, is an all-female species that reproduces by gynogenesis, i.e., it relies on sperm of males of closely related species to trigger embryogenesis. Sperm is supplied by males of P. latipinna and P. mexicana. Amazon mollies live in sympatry with at least one of these species, a few populations live in sympatry with two sperm-donor species. As P. formosa is sperm dependent, it needs mechanisms for species and mate recognition. To investigate the effect of rearing conditions on sexual preferences of Amazon mollies, we raised Amazon mollies in sympatry with P. latipinna and P. mexicana males. We used simultaneous choice tests to determine the effect of age on female sexual preferences. Immature Amazon mollies do not exhibit a preference if given a choice between a P. latipinna and a P. mexicana male, whereas adult P. formosa do have a preference for the P. latipinna male. We used two different stimuli in this study, live males and videotapes of males.
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    Spawning Season Variations of Female Nile Tilapia, Oreochromis niloticuss, From Man-made Lakes of Côte D'Ivoire (1999)
    Springer
    Environmental biology of fishes 56 (1999), S. 375-387 
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    ISSN: 1573-5133
    Keywords: seasonality ; inter-annual variations ; fish ; cichlid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spawning season of Oreochromis niloticus females was studied over two annual cycles in 6 small agropastoral and 2 large hydroelectric reservoirs of Côte d'Ivoire (Ayamé and Kossou), situated between 5 and 10°N of latitude. Reproduction occurred during a marked season in the agropastoral reservoirs and in Lake Ayamé, whereas it was continuous in Lake Kossou. Spawning season differed between reservoirs and among years within the same reservoir. Seasonal changes in temperature, rainfall, day length, chlorophyll a concentration and water level often corresponded with changes in the annual spawning cycle. However, annual periodicity of O. niloticus reproduction was more likely influenced by the ephemerides cycle.
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    Variations in age and size at maturity of female Nile tilapia, Oreochromis niloticus, populations from man-made lakes of Côte d'Ivoire (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 453-465 
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    ISSN: 1573-5133
    Keywords: phenotypic plasticity ; reproductive style ; fish ; cichlid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reproductive characteristics of Oreochromis niloticus females were studied in two large hydroelectric dams and 6 small agropastoral reservoirs of Côte d'Ivoire, selected for their diversity of environmental conditions and sizes (6 to 80000 ha). Comparative analysis of age and size at maturity revealed large differences between the populations with early maturity, late maturity, and intermediate situations. All the populations matured in their first year, between 5.6 and 10 months. Age and size at maturity were positively correlated with the reservoir area. The range of variation in age at maturity between populations was far greater than that of size at maturity. However, size at maturity also appears to be very plastic as intra-population variations of 2 to 3 cm were found between consecutive years. A comparison of age at maturity for a population in 1994 and 1996 showed that this trait is also likely to vary significantly at the intra-population level. Environmental factors which could potentially affect age and size at maturity are discussed. Growth differences are the probable explanation for the observed patterns of variation between populations. Rapid changes in age and size at maturity at inter or intra-population levels suggest that the observed variations might be explained by differences in environmental variables (phenotypic plasticity) rather than by genetic differences.
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    Dissolved oxygen and fish distribution in a Florida spring (1998)
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    Environmental biology of fishes 53 (1998), S. 211-223 
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    ISSN: 1573-5133
    Keywords: artesian spring ; Poeciliidae ; respiratory ecology ; hypoxia ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examined the distribution and relative abundance of fishes along a dissolved oxygen gradient in Singing Springs, Florida. Over the 1-year study, dissolved oxygen concentration in the spring exhibited a strong gradient ranging from an average of 0.20 mg l–2AM1 at the boil to 1.81 mg l–2AM1 110 meters downstream. Seasonal variation in dissolved oxygen was very low relative to the spatial variation along the spring gradient. Fish community composition was evaluated monthly at the boil of the spring, 45 m downstream just after the confluence of the spring and the main river, and 110 m downstream. The fish community in the spring was characterized by species generally considered to be tolerant of low oxygen. Gambusia holbrooki was the most abundant species at all sites comprising an average of 88.1% of the fish captured at the boil, 63.2% of the fish captured at 45 m, and 74.8% of the fish captured at 110 m downstream. The diversity of fishes (G. holbrooki, Heterandria formosa, Notropis harperi, Lucania goodei, and Poecilia latipinna) increased with distance from the boil. Although there were some seasonal differences in patterns of diversity and community structure, the inter-site differences were much more apparent throughout the study. It is likely that the pattern of variation in dissolved oxygen interacts with the respiratory abilities of the fishes to affect the distribution pattern and community composition along the gradient.
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    Reproduction, diet and population structure of the mountain mullet, Agonostomus monticola, in Jamaica, West Indies (1998)
    Springer
    Environmental biology of fishes 53 (1998), S. 347-352 
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    ISSN: 1573-5133
    Keywords: size at maturity ; spawning ; sex ratios ; fecundity ; diet ; population structure ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproduction, feeding and population structure were investigated in the mountain mullet, Agonostomus monticola, in eastern Jamaica between 1982 and 1986. Female fishes just outnumbered males 1.2 : 1. Minimum size at maturity for females was 123 mm fork length (FL) and 96 mm FL for males. Mean size at maturity for females was 165.8 mm FL (S.D.=1.61) and for males was 148.4 mm FL (S.D.=2.97). Fecundity was 340 000 eggs for a 25 g ovary. Fecundity (F) was related to size by the equation F=153.8 FL1.36. Mean lengths of males and females captured by all methods were 129.4 mm (S.D.=5.56) and 160.4 mm FL (S.D.=0.70), respectively. A. monticola was found to be chiefly an insectivorous feeder. The major food items found in stomach contents in ranked sequence were insects, freshwater prawns, plant detritus and algae.
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    Life History of Black Seabream, Spondyliosoma cantharus, off the Canary Islands, Central-east Atlantic (1999)
    Springer
    Environmental biology of fishes 54 (1999), S. 325-336 
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    ISSN: 1573-5133
    Keywords: population structure ; reproduction ; growth ; mortality ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Black seabream, Spondyliosoma cantharus, caught off the Canary Islands is characterized by a protogynous hermaphroditism. The size range of the catches is between 8 and 40 cm, with a main distribution between 16 and 24 cm. The mean length of the individuals shows an increase with increasing depth. Males:females ratio is unbalanced in favour of females (1:2.18). The reproductive season extends from late autumn to mid spring, with a peak in spawning activity in January–February. A dichromatism is found between males and females during the spawning season. Males reach maturity at a larger total length, 22.7 cm (3 years old), than females, 17.3 cm (2 years old). Morphometric relationship between length and mass for the whole population is described by the parameters: a=0.00732, and b=3.24747. Otoliths age readings indicate that the exploited population consists of eleven age groups (0–X years), including a very high proportion of individuals between 2 and 3 years old. The von Bertalanffy growth parameters for the whole population are: L∞=43.35 cm, k=0.24 year−1, and t0=−0.11 year. The rates of total, natural and fishing mortality are 1.36, 0.52 and 0.84 year−1, respectively. The length at first capture is 16.8 cm. The exploitation rate indicates that the stock is overfished.
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    Ontogeny of somatolactin mRNA in the gilthead sea bream Sparus aurata (1997)
    Springer
    Fish physiology and biochemistry 17 (1997), S. 247-252 
    Details
    ISSN: 1573-5168
    Keywords: somatolactin ; growth hormone ; mRNA ; Northern ; fish ; Sparus aurata ; embryos ; larvae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Expression of somatolactin (SL) gene during embryonal and early stages of larval development of the teleost Sparus aurata was determined by Northern blot analysis. Poly(A+)RNA was prepared from a pool of embryos collected at early and late stages or from larvae collected on different days after hatching. When hybridized to Sparus aurata SL cDNA, SL specific mRNA was seen both in embryos and in larvae. Levels of SL increased from day 1 onwards and reached the highest levels on day 21. Re-hybridization with Sparus aurata growth hormone (GH) cDNA revealed GH specific mRNA first on day 6 post-hatching. Levels of GH increased to maximal levels on day 10 and then decreased on days 15 and 21, thereby confirming the pattern of GH expression (Funkenstein and Cohen 1996). The patterns of SL and GH gene expression are different in gilthead sea bream during embryonal and larval development. Furthermore, the presence of SL transcript in embryos, prior to pituitary gland development, suggests the possibility that SL mRNA of maternal origin may be present in the oocyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007714409674
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    Endocrine stress response and abnormal development in carp (Cyprinus carpio) larvae after exposure of the embryos to PCB 126 (1998)
    Springer
    Fish physiology and biochemistry 18 (1998), S. 321-329 
    Details
    ISSN: 1573-5168
    Keywords: fish ; early development ; PCB 126 ; ACTH ; α-MSH ; cortisol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To investigate whether PCB 126 exposure duringembryonic development induces an endocrine stressresponse in larval carp, eggs were exposed,containing 0.01% ethanol (vehicle-control), 10-11,immediately after fertilization, for 48 h to water10-10 or 10-9 mol l-1 PCB in 0.01% ethanol. Eggsincubated in water served as controls. After transferto PCB-free water, mortality, the incidence ofyolk-sac and pe-ricardial oedema, wet and dry weight,rate of skin pigmentation, and whole-body contents ofthe stress hormones ACTH, α-MSH and cortisol weredetermined at 48, 96, 144, 168, 192 and 216 hpost-fertilization. Except for the dry weight, allparameters of animals exposed to 10-10 and 10-9 moll-1 PCB increased in a concentration-related manner.However, these changes became evident only at 144 hpost-fertilization, i.e. after resorption of theyolk-sac. Swelling of the yolk sac and pericardiumoccurred, and whole-body ACTH, α-MSH and cortisollevels increased. Although animals exposed to 10-10and 10-9 mol l-1 PCB displayed stable but elevatedwhole-body ACTH and α-MSH levels until 216 h,whole-body cortisol concentrations gradually decreasedfrom 168 h post-fertilization, and were significantlybelow control values at 216 h post-fertilization.Exposure of the carp embryos to 10-11 mol l-1 PCB only increased whole-body α-MSH levels. Increased whole-body ACTH and cortisol levels indicate that PCBinduces a stress response in carp larvae, possiblymediated by a disturbed hydromineral balance (oedema).We further suggest that the PCB-stimulated bodypigmentation is mediated by a stimulation of α-MSHsecretion.
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    URL: http://dx.doi.org/10.1023/A:1016076415178
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    Effects of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus (1999)
    Springer
    Fish physiology and biochemistry 21 (1999), S. 249-255 
    Details
    ISSN: 1573-5168
    Keywords: diet ; lipid ; oxidative stress ; α-tocopherol ; cytochrome P450 ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was conducted to evaluate the effects of different concentrations of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus. Diets were formulated to contain 40% crude protein from solvent-extracted menhaden fish meal and 0, 7, 14 or 21% lipid from menhaden fish oil. The basal diet, without supplemental fish oil, contained lipid at 0.4% of dry weight. The diets were fed to groups of 25 juvenile red drum initially averaging 7.3 ± 0.18 g fish−1 in a recirculating culture system for 8 weeks and weight gain was recorded. After an additional 8 weeks, 16 fish from each treatment were sacrificed and the following measurements were recorded: hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and liver α-tocopherol, malondialdehyde (MDA) formation, and cytochrome P-4501A activity (measured as 7-ethoxyresorufin O-deethylase (EROD) activity). The activity of alanine and aspartate aminotransferases and concentrations of α-tocopherol also were measured in plasma. Weight gain was significantly (p〈0.05) affected by dietary lipid concentration, with values ranging from 361% of initial weight for fish fed the basal diet to 527% of initial weight for fish fed the diet containing 7% lipid. The HSI and IPF ratio values also were significantly affected by lipid with the lowest values recorded for fish fed the basal diet and the highest values observed in fish fed the diet containing 21% lipid. Increasing dietary lipid significantly increased oxidative stress as reflected in reduced α-tocopherol in liver and plasma and increased MDA formation in the liver, although no overt pathological signs were observed. These findings suggest that lipid concentrations between 7 and 14%, when the diet contains 60 IU vitamin E kg−1, are likely to limit oxidative stress and result in normal physiological responses of red drum.
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    URL: http://dx.doi.org/10.1023/A:1007843420128
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  • 88
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    Intracellular pH regulation of rainbow trout and carp thrombocytes (1999)
    Springer
    Fish physiology and biochemistry 21 (1999), S. 269-275 
    Details
    ISSN: 1573-5168
    Keywords: acid-base regulation ; catecholamines ; fish ; sodium-dependent bicarbonate transport ; sodium/proton exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pH regulation of rainbow trout and carp thrombocytes was investigated using the pH-sensitive fluorescent dye BCECF and a PTI Imagescan image analysis system. The cells were experimentally acidified either using the ammonium chloride prepulse method or perfusing the cells with a saline containing propionate ion. The recovery from the acidification was followed. By using ion substitutions (N-methyl-D-glucamine for sodium; TRIS vs carbon dioxide/bicarbonate buffer) and transport inhibitors (amiloride to inhibit sodium/proton exchange and DIDS to inhibit chloride and bicarbonate dependent acid extrusion mechanisms) the transport pathways were identified. The pH regulatory mechanisms of thrombocytes in both species were similar. The pH recovery after experimental acidification was fully inhibited by removing sodium from the medium. The sodium-dependent acid extrusion had both amiloride-sensitive and DIDS-sensitive components, indicating that both sodium/proton exchange and sodium-dependent bicarbonate transport were involved. The role of sodium-dependent bicarbonate movements in pH regulation was ascertained by showing that pH recovery occurred faster at a high than at a low bicarbonate concentration. Adrenergic stimulation did not affect the intracellular pH.
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    URL: http://dx.doi.org/10.1023/A:1007856808003
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    The presence of uric acid, an antioxidantive substance, in fish seminal plasma (1999)
    Springer
    Fish physiology and biochemistry 21 (1999), S. 313-315 
    Details
    ISSN: 1573-5168
    Keywords: antioxidants ; fish ; spermatozoa ; seminal plasma ; urate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract High concentrations of uric acid in seminal plasma of a range of teleost fish species are reported for the first time. Concentrations of urate amounted to 223.4; 121.9–130.0, 355.9, 735.6, 124.0, 192.7 and 148.0 μM for rainbow trout (Oncorhynchus mykiss), yellow perch (Perca flavescens), muskellunge (Esox masquinongy), Northern pike (Esox lucius), carp koi (Cyprinus carpio), bream (Abramis brama), and tench (Tinca Tinca), respectively. Uric acid is an important anti-oxidant, therefore, it has a potential role in protection of fish spermatozoa against oxidative damage.
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    URL: http://dx.doi.org/10.1023/A:1007886121663
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  • 90
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    Effects of growth hormone on plasma ionic regulation, respiration and extracellular acid-base status in trout (Oncorhynchus mykiss) transferred to seawater (1995)
    Springer
    Fish physiology and biochemistry 14 (1995), S. 279-288 
    Details
    ISSN: 1573-5168
    Keywords: fish ; Oncorhynchus mykiss ; growth hormone ; GH ; seawater adaptation ; acid-base status ; oxygen consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of trout recombinant growth hormone (rtGH) treatment (0.25 μg g−1 by intraperitoneal implant) on plasma ionic regulation, extracellular acid-base status and respiration were investigated in freshwater rainbow trout and during a 4-day period after direct transfer into seawater (35 g 1−1). In freshwater, rtGH treatment resulted in a significant increase in gill (Na+, K+) ATPase activity and in standard metabolism (MO2). The latter would mainly result from a higher rate of protein synthesis. Direct transfer from freshwater to seawater induced a decrease in arterial blood pH, far more pronounced in controls than in treated fish. This effect could be regarded in both groups mainly as a metabolic acidosis resulting from extracellular ion composition changes (i.e., an increase higher in chloride than in sodium, more marked in controls than in treated fish). As the rise in PaCO2, in spite of an increase in ventilatory activity, is more significant in controls than in treated fish, it can be assumed that rtGH treatment lightened the decrease in the gas diffusing capacity of gills induced by transfer to seawater. The initial increase in MO2 in both controls and treated fish could be the consequence of an increase in energetic cost of ventilation and osmoregulation. Then, in treated fish, the persistent high level of M may indicate a stimulation of intermediary metabolism by rtGH. In addition, the absence in treated fish of an increase in plasma lactate concentration, as observed in controls, would indicate that rtGH attenuated the decrease in O2 affinity of haemoglobin foreseeable from the metabolic acidosis.
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    URL: http://dx.doi.org/10.1007/BF00004066
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    Effects of diet on spontaneous locomotor activity and oxygen consumption in Adriatic sturgeon (Acipenser naccarii) (1995)
    Springer
    Fish physiology and biochemistry 14 (1995), S. 341-355 
    Details
    ISSN: 1573-5168
    Keywords: diet ; fish ; hypoxia ; O2 uptake ; spontaneous locomotor activity ; sturgeon ; ω3 fatty acids ; vitamin E
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adriatic sturgeon (Acipenser naccarii) were maintained on a commercial diet enriched either in long chain polyunsaturated fatty acids of the ω3 series (ω3 LCPUFA) or in saturated fatty acids (SFA). The effects of dietary fatty acid composition on spontaneous locomotor activity in normoxia and hypoxia (O2 tension = 10.5 ± 0.8 kPa), and on oxygen consumption (MO 2) in normoxia, in hypoxia (O2 tension = 6.6 ± 0.8 kPa) and during recovery were then investigated. The effects of adding supplementary vitamin E to the fat-enriched diets were also studied. Dietary fatty acid composition had effects on spontaneous locomotor activity and MO 2 in normoxia. Activity levels were higher in all sturgeon fed extra dietary fats (without vitamin E), when compared with control animals, but fish fed ω3 LCPUFA had a significantly lower MO 2 than those fed SFA, with intermediate MO 2 in controls. In hypoxia, sturgeon ω3 LCPUFA did not alter activity or MO 2 whereas those fed SFA reduced both and controls reduced MO 2. During recovery, both animals fed SFA and controls had a higher MO 2 than sturgeon fed ω3 LCPUFA. The data indicate that fish fed ω3 LCPUFA are more tolerant of hypoxia than controls or those fed SFA, as they did not reduce either activity or MO 2, and consumed less O2 during recovery. Vitamin E supplements modified the effects elicited by dietary fats. All sturgeon fed vitamin E had low activity levels in normoxia and hypoxia. Sturgeon fed vitamin E with ω3 LCPUFA had a higher MO 2 in normoxia than those fed ω3 LCPUFA alone; reduced MO 2 in hypoxia, and during recovery increased MO 2 to a rate higher than that of animals fed ω3 LCPUFA alone. In normoxia, sturgeon fed vitamin E with SFA had a similar MO 2 to those fed SFA alone but did not change MO 2 in hypoxia or during recovery. Thus, the effects of vitamin E were dependent on fat composition of the diet. Vitamin E with ω3 LCPUFA removed the beneficial effects on MO 2 and responses to hypoxia obtained with ω3 LCPUFA alone, but vitamin E with SFA allowed sturgeon to maintain aerobic metabolism in hypoxia, a more effective response than that observed in fish fed SFA alone.
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    URL: http://dx.doi.org/10.1007/BF00003373
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    Effects of season and dietary ascorbic acid on some biochemical characteristics of rainbow trout (Oncorhynchus mykiss) semen (1996)
    Springer
    Fish physiology and biochemistry 15 (1996), S. 1-10 
    Details
    ISSN: 1573-5168
    Keywords: fish ; vitamin C ; spermatozoa ; seminal plasma ; proteinase inhibitors ; aspartate aminotransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the reproductive season, rainbow trout spermatozoa are stored in the sperm ducts for several months. There is no sperm production at this time since spermatogenesis is completed before spawning. To leam more about characteristics of semen during such a long storage, we analyzed changes in protein concentrations, anti-proteinase activity in seminal plasma and sperm aspartate aminotransferase activity during an extended reproductive period during which fish were fed diets supplemented with various ascorbic acid concentrations. Seminal plasma protein concentration and anti-proteinase activity declined toward the end of the reproductive season. These phenomena may be related to oncoming proteolytic events leading to degradation of the sperm. Protein concentrations and anti-proteinase activities were strongly correlated within groups of different ascorbic acid supplementations and several sampling dates (r=0.6–0.9 in most cases, p〈0.05). Ascorbic acid deficiency resulted in a decrease in both parameter levels as compared to levels in groups with vitamin C supplement (p〈0.08). Deficiency also resulted in lower stimulation of aspartate aminotransferase by an exogenous pyridoxal 5′-phosphate in comparison to fish fed vitamin C-supplemented diets (p〈0.05). These results support earlier studies suggesting a protective role of ascorbic acid toward maintaining sperm quality.
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    URL: http://dx.doi.org/10.1007/BF01874832
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    Distribution of glutamine synthetase in the snapper (Pagrus auratus) and implications for the immune system (1996)
    Springer
    Fish physiology and biochemistry 15 (1996), S. 187-194 
    Details
    ISSN: 1573-5168
    Keywords: glutamine ; glutamine synthetase ; immunity ; stress ; teleost ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A sensitive radiotracer method was used to detect glutamine synthetase activity in fish. The distribution of glutamine synthetase activity using this method was shown to be widespread in organs and tissues of the marine finfish, snapper,Pagrus auratus. The optimum pH and temperature for glutamine synthetase activity and Km of glutamate from the brain of the snapper are also reported. Interestingly no glutamine synthetase activity was detected in lymphoid organs, indicating, that as in the mammal, the teleostean immune system is likely to rely on glutamine in circulation for energy and nucleotide synthesis. Furthermore circulating glutamine levels fell as fish became stressed or became ill. Implications of these observations on the function of the immune system of fish are discussed.
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    URL: http://dx.doi.org/10.1007/BF01875569
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    When Do Environment–recruitment Correlations Work? (1998)
    Springer
    Reviews in fish biology and fisheries 8 (1998), S. 285-305 
    Details
    ISSN: 1573-5184
    Keywords: correlation ; environment ; fish ; meta-analysis ; recruitment ; variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract I review the role of environmental variability in the survival of juvenile fish and shellfish by examining the success of previously published environment–recruitment correlations when tested with new data. The proportion of published correlations that have been verified upon retest is low. There is one generalization that stands out: correlations for populations at the limit of a species' geographical range have often remained statistically significant when re-examined. An examination of environment–recruitment correlations that were reviewed 13 years ago by Shepherd and co-workers shows that only 1 out of 47 reviewed studies is currently used in the estimation of recruitment in routine assessments. The results suggest that future progress will require testing general hypotheses using data from many populations.
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    URL: http://dx.doi.org/10.1023/A:1008828730759
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    What is a fish species? (1999)
    Springer
    Reviews in fish biology and fisheries 9 (1999), S. 281-297 
    Details
    ISSN: 1573-5184
    Keywords: fish ; gene flow ; hybridization ; molecular phylogenetics ; speciation ; species concepts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The formal processes of alpha-taxonomy ensure that species have uniquenames and can be identified. No similar process is mandatory forinfraspecific variation, so the species is a uniquely importantpractical term. At present, there is little agreement of the definitionof a species. In the last 30 years, numerous concepts have beenproposed. The nature of fish species is reviewed. Clonal inheritance ofnuclear genes occurs in several lineages. Hybridization is frequent,often leading to introgression, which may lead to extinction of species.Species may have hybrid origins. There is good evidence for parallelspeciation in similar habitats. There are clearly exceptions to thecladistic assumption of dichotomous branching during speciation. Siblingspecies may exist with no discernible niche differentiation. Basic assumptions are violated for the recognition, phylogenetic,ecological and some formulations of the evolutionary species concepts.The most satisfactory definitions are two of the earliest proposed inthe light of evolutionary theory. The Darwinian view is that species arerecognizable entities which are not qualitatively distinct fromvarieties. A restatement of this concept in genetic terms provides ameans of dealing with all forms of species known in present-day fishes.This modified Darwinian concept is operated through the application offuzzy logic rather than rigid definition. This involves a search fordiscontinuities between species, rather than an a priori definition ofhow boundaries are to be determined. A subset of Darwinian species areMayrian or ‘biological species’, which are characterized by theirdemonstrable reproductive isolation from other species. The status of apopulation as a Mayrian species is a testable hypothesis. Moleculartechniques allow this hypothesis to be tested more easily thanpreviously, at least when dealing with sympatric populations.
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    URL: http://dx.doi.org/10.1023/A:1008903228512
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    Drift ecology of western catostomid larvae with emphasis on Warner suckers, Catostomus warnerensis (Teleostei) (1997)
    Springer
    Environmental biology of fishes 49 (1997), S. 187-195 
    Details
    ISSN: 1573-5133
    Keywords: Pleistocene lakes ; drift behavior ; Catostomidae ; fish ; larvae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied drift ecology of Warner sucker, Catostomus warnerensis, larvae in streams of Warner Valley, Oregon in 1992 and 1993 in part to determine whether downstream transport of larvae limits juvenile recruitment. Variation in runoff for the two years was extreme, where peak discharge in 1992 was two orders of magnitude lower than peak discharge in 1993. We deployed drift nets in low-gradient stream sections that are modified by diversions. Low catches of drifting sucker larvae (zero in 1992 and two in 1993) indicate that losses into diversions were probably minimal. In 1992, we conducted in situ experiments to determine how sucker larvae behaved when exposed to high velocity current by placing individuals of various sizes in mid-channel and tracking drift responses by snorkeling. Even the smallest larvae used did not drift far (2.6 m) or for very long (0.97 min), as they resisted downstream transport by exploiting cover provided by aquatic plants and debris. We also recorded locations of larvae during a 24-hour cycle to determine whether positions occupied during the day changed at night. We found that groups were positioned closer to shore at night in 1993 than in 1992, suggesting that larvae reduced the likelihood of becoming entrained into swift current by moving away from mid-channel at night when visual orientation is impaired. These patterns of drift avoidance are different from behaviors of other western catostomid larvae, potentially because terminal lake habitat in Pleistocene basins such as the Warner Valley has been unreliable.
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    URL: http://dx.doi.org/10.1023/A:1007329010680
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    Effects of salinity on survival, growth, metabolism, and behavior in juvenile hogchokers, Trinectes maculatus fasciatus (Achiridae) (1997)
    Springer
    Environmental biology of fishes 49 (1997), S. 323-331 
    Details
    ISSN: 1573-5133
    Keywords: osmoregulation ; migration ; life history pattern ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To understand the biological significance of the southern hogchoker's seasonal migration pattern, the effects of salinity (0, 7 and 15 ppt) on survival, growth, metabolism, and behavior were examined. Survival averaged 96% and salinity did not affect (p = 0.25) the growth rates of juvenile hogchokers during the 60 day experimental growth period. However, oxygen consumption rates suggest that juvenile metabolism is influenced by salinity. Circadian patterns of metabolic rates were present in the 7 and 15 ppt treatments, but absent in the freshwater group. The juveniles in the 7 ppt treatment exhibited significantly (p 〈 0.05) lower overall rates than the freshwater fish, while the fish in the 15 ppt condition had intermediate metabolic rates. Juvenile hogchokers also showed shifts in diel activity and feeding patterns among salinities, with the active time period shortening with increasing salinity. The main conclusion is that juvenile salinity intolerance is not the driving mechanism of their migration pattern, but salinity does affect juvenile metabolism and behavior. The metabolic effects of salinity can explain summer migration in juvenile hogchokers. Additionally, the shifts in their behavioral responses can generally be explained by the summer migration movements.
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    The influence of salinity on ionic concentrations and osmolarity of blood serum in lake sturgeon, Acipenser fulvescens (1998)
    Springer
    Environmental biology of fishes 52 (1998), S. 477-482 
    Details
    ISSN: 1573-5133
    Keywords: osmoregulation ; ionoregulation ; Acipenseridae ; Moose River ; habitat ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examined the extent to which lake sturgeon, Acipenser fulvescens, regulated serum ion concentrations and osmolarity in relation to ambient salinity. Twenty juvenile lake sturgeon, brood stock from the Moose River in the Hudson Bay drainage basin, were gradually transferred from freshwater to more saline waters at a rate of 2‰ day-1. Blood was sampled from fish at 0, 10, 15 and 25‰ following 48 h acclimation periods. Concentrations of Na+, K+, Cl-, Ca2+ and osmolarity were measured. Experimentation was terminated at 25‰ due to poor fish health resulting in two mortalities. Within freshwater, lake sturgeon blood serum displays similar osmotic and ionic composition to other North American species of sturgeon. Juvenile lake sturgeon do not appear capable of homeostasis above 15‰ nor are they tolerant to environments exceeding 25‰. Some evidence of greater tolerance to elevated salinities with increased size was noted. The ecological potential for resource exploitation in regions of elevated salinities is discussed.
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    URL: http://dx.doi.org/10.1023/A:1007421410090
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    The use of polynomial regression analysis with indicator variables for interpretation of mercury in fish data (1998)
    Springer
    Biogeochemistry 40 (1998), S. 189-201 
    Details
    ISSN: 1573-515X
    Keywords: binary variables ; fish ; impoundment ; indicator variables ; James Bay ; mercury ; polynomial regression ; Québec ; reservoirs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Mercury levels in fish in reservoirs and natural lakes have been monitored on a regular basis since 1978 at the La Grande hydroelectric complex located in the James Bay region of Québec, Canada. The main analytical tools historically used were analysis of covariance (ANCOVA), linear regression of the mercury-to-length relationship and Student-Newman-Keuls (SNK) multiple comparisons of mean mercury levels. Inadequacy of linear regression (mercury-to-length relationships are often curvilinear) and difficulties in comparing mean mercury levels when regressions differ lead us to use polynomial regression with indicator variables. For comparisons between years, polynomial regression models relate mercury levels to length (L), length squared (L2), binary (dummy) indicator variables (Bn), each representing a sampled year, and the products of each of these explanatory variables (L × B1, L2 × B1, L × B2, etc.). Optimal transformations of the mercury levels (for normality and homogeneity) were found by the Box-Cox procedure. The models so obtained formed a partially nested series corresponding to four situations: (a) all years are well represented by a single polynomial model; (b) the year-models are of the same shape, but the means may differ; (c) the means are the same, but the year-models differ in shape; (d) both the means and shapes may differ among years. Since year-specific models came from the general one, rigorous statistical comparisons are possible between models. Polynomial regression with indicator variables allows rigorous statistical comparisons of mercury-to-length relationships among years, even when the shape of the relationships differ. It is simple to obtain accurate estimates of mercury levels at standardized length, and multiple comparisons of these estimations are simple to perform. The method can also be applied to spatial analysis (comparison of sampling stations), or to the comparison of different biological forms of the same species (dwarf and normal lake whitefish).
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    URL: http://dx.doi.org/10.1023/A:1005997430906
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  • 100
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    Fish mercury levels in relation to characteristics of hydroelectric reservoirs in Newfoundland, Canada (1998)
    Springer
    Biogeochemistry 40 (1998), S. 217-233 
    Details
    ISSN: 1573-515X
    Keywords: Canada ; fish ; hydroelectric reservoirs ; mercury ; Newfoundland ; return time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Mercury levels in fish have been demonstrated to increase after impoundment with augmented levels of mercury predicted to decline as the reservoir ages. Previous research in Newfoundland predicted return rates in the order of 10 to 12 years for landlocked Atlantic salmon or ouananiche (Salmo salar) and 7 years for brook trout (Salvelinus fontinalis). In order to test the validity of these predictions on a broader spatial and temporal scale, and develop more generally predictive ‘models’, mercury levels in three fish species were studied in 16 older Newfoundland hydroelectric reservoirs of various age (32 to 95 years) and area flooded (21 to 13,000 ha). Mercury concentrations were standardized to fish length and correlated with physical, chemical, and biological characteristics of the sampling sites. Standard length mercury levels ranged from 0.23 to 0.86 ppm in ouananiche, 0.13 to 0.59 ppm in brook trout, and 0.22 to 0.72 in arctic charr (Salvelinus alpinus). Fish in excess of the Canadian Safety Limit (0.5 ppm) were collected from 14 of 16 sites for ouananiche, 8 of 17 sites for brook trout, and 3 of 7 sites for arctic charr, including control lakes. Standard length fish mercury levels were correlated with reservoir age and (log10) area flooded for ouananiche and with pH for arctic charr. A multiple regression model was developed relating standard length mercury in ouananiche with reservoir age and log10 of the flooded area. There were no apparent relationship between reservoir characteristics and brook trout mercury concentrations. Based on this analysis, it is not possible, at present, to develop generally predictive models for all species found in Newfoundland impoundments.
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    URL: http://dx.doi.org/10.1023/A:1005975714493
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